Similar Institutions
On this page, the Math Factory Working Group collects information concerning similar institutions. There are mathematics museums in other countries, other institutions in the U.S. with mathematics content, and traveling exhibitions devoted to mathematics.
Interactive mathematics museums abroad

Mathematikum. Giessen, Germany. mathematikum.de
This handson museum dedicated to mathematics contains roughly 100 interactive exhibits in 10,000 square feet of exhibit space, ranging from simple geometric puzzles to mathematical sculptures to a display in which one writes a musical composition by rolling dice. It serves as a wonderful demonstration of what an interactive museum of mathematics can be, and should serve as a model for us. Areas MoMath might consider differentiating on are the integrated use of technology, and the connection of the exhibits together thematically and with traditional curriculum topics so that visitors obtain a better understanding of what mathematics is and why it is both important and fun. 
Math museum in Seoul Korea.
This wonderful handson interactive math museum was founded by Chang Hoon. They sell exhibits at their website, http://mathlove.com 
The Garden of Archimedes, Florence, Italy. web.math.unifi.it/archimede
This beautiful museum of mathematics has three main permanent galleries, devoted to the mathematics of curves, to the Pythagorean Theorem, and the history of mathematics from the Islamic world through Renaissance Italy to the modern world.  Mathematics Adventure Land, (Erlebnisland Mathematik), Dresden, Germany.Â http://www.math.tudresden.de/alg/erlebnisland/en/start.html Handson museum with over 100 interactive exhibits.

Arithmeum, Bonn, Germany, http://www.arithmeum.unibonn.de/en/
Historical calculating machines and historical arithmetic books dating back to Gutenberg's times. 
MiMa, Museum for Minerals and Mathematics Oberwolfach, http://www.mima.museum/museum.php
Originally just minerals, has branched out into mathematics in part because of the worldrenowned math conference center in Oberwolfach. Creator of the math exhibit "Imaginary".  Mathemuseum Stams, Austria http://mathemuseum.org
 Haus der Mathematik, Vienna, Austria http://www.hausdermathematik.at/

The Mathematics Museum (Japan). mathmuse.sci.ibaraki.ac.jp/indexE.html
Another interactive museum dedicated to mathematics, this one has a much more elaborate web site in terms of mathematical content, although less information (at least on the English pages) about the museum itself.  MMACA: Museu de MatemÃ tiques de Catalunya, http://www.mmaca.cat/, photos: http://picasaweb.google.com/Josep.Rey/Mmaca2009?authkey=Gv1sRgCPPApmTu39ywE&feat=directlink#

Mathematics Palace, BorÃ¥s, Sweden. http://www.navet.com/sida.aspx?id=1080
This appears to be a portion of a larger science center in Sweden, but nevertheless a sizable portion (500 square meters, or roughly 5000 square feet) of exhibition space devoted exclusively to mathematics. 
Magical Mathematics Museum, Calgary, CA. gamesbygord.blogspot.com
This museum proposal by Gordon Hamilton appears to have remained at the conceptual stage but comprised many very interesting ideas. 
Palace of Discovery, Paris, France. www.palaisdecouverte.fr
This highlyregarded science museum is not solely devoted to mathematics, but unlike most U.S. science museums, mathematics occupies a prominent place. On their home page, you will see a "Mathematics" button which leads to descriptions of three galleries: the Pi Room, the Mathematical Surfaces collection, and the Mathematics Room, focusing on polyhedra and mathematics in nature. 
iQ Park. Liberec, Czech Republic, outside of Prague. www.iqpark.cz (note the tiny British flag in the upperright corner if you are looking for the Englishlanguage pages, which have noticeably less content than the Czech pages.)
gallery of photographs (link generously provided by Brett Kuehner; browse forward for about 15 photos) that math and math puzzles play a larger role at iQ than at most handson science museums, certainly as compared to such museums in the U.S.  Explora, the museum of the 3rd dimension.Â Frankfurt, Germany http://www.exploramuseum.de/Â Although this museum has a great deal of of purely visual/artistic content, optical illusions, etc., there is a significant amount of real mathematical interest, such as a nice physical interactive showing a variety of possible ruled surfaces.
 Deutsches Museum, Munich, Germany, http://www.deutschesmuseum.de/en/exhibitions/naturalsciences/mathematics/ includes a Mathematical Cabinet exhibit with "a fine collection of geometrical objects/sculptures".
 Puzzlemania Maths exhibition. There is a description of this on Ben Craven's website. http://bencraven.org.uk/maths_exhibition.html
 Exhibits http://matemateca.ime.usp.br/ (without a permanent building) in Brazil; text in Portuguese.
 Matematica Viva, Lisbon, http://www.pavconhecimento.pt/exposicoes/permanentes/
 Laboratorio di Matematica and Teatrum Machinarum, Modena, Italy, http://www.museo.unimo.it/theatrum/macchine/_00prefing.htm
 Math Fitness, Genoa, Italy, http://www.matefitness.it/ It's not quite clear if this organization has any permanent exhibition space, but it has created traveling exhibitions, sponsored outdoor math programs, seems to have dedicated math classrooms, and is very dedicated to many different kinds of interactive programming.
 A list of additional European exhibits is here: http://phobos.xtec.cat/creamat/mmaca/index.php?option=com_content&task=blogsection&id=4&Itemid=31 (I'm not sure which are permanent and which are traveling.)
 Small Math Museum at Technical University of Munich. There are many pictures here, but only German text: http://wwwm10.ma.tum.de/ixquadrat/. More information can be obtained from the organizer, Prof. Jurgen RichterGeber, http://wwwm10.ma.tum.de/bin/view/Lehrstuhl/RichterGebert.
 The Math Museum of Eötvös University Budapest, Hungary. A collection of many polyhedral models, books, journals, and other mathematical paraphenalia in an exhibition room at the University. Contact Sándor Kabai www.kabai.hu
 Techniquest, Cardiff, Wales, has a significant collection of mathematical exhibits and large puzzles. http://www.techniquest.org/business/content/pdf.html?h=Exhibits > Maths &file=pdfs/Exhibits/Themes/MathsTheme.pdf
Mathematics traveling exhibitions
 Our very own Math Midway, of course.
 Math Alive! â€” a new traveling exhibition being created by Evergreen Exhibitions.

Flip It, Fold It, Figure It Out: Playing with Math astc.org/exhibitions/flipit/dflipit.htm
This exhibition developed by the Museum of Life and Science in Durham, NC â€” touches on origami, quilting, tiling patterns, music, and more.  Design Zone by the Oregon Museum of Science and Industry. http://www.omsi.edu/designzoneexhibit

Fun, 2, 3, 4: All about a number of things! sciencenter.org/exhibits/default_fun234.asp
The Ithaca Sciencenter designed this exhibition with interactive activities for ages 512 that focus primarily on counting and measurement. 
Geometry Playground: An Immersive Learning Laboratory informalscience.org/project/show/683
The Exploratorium is developing this exhibition in conjunction with a significant research effort on spatial and mathematical learning. 
Nature's Numbers
This exhibition designed by the Franklin Institute covers 600800 square feet and has 20 activities in four stations, covering "Repeating Patterns", "Shapes and Sizes", "Designs in Nature", "Mathematical Inquiry" 
The Math Expo. An international traveling exhibit, with a web presence. experiencingmaths.org, mathex.org
This exhibit has toured South America and Asia, I believe it originated in Europe, but as far as I know it has not come to North America.  Pizza: Any Way You Slice It! Created by the Omaha Children's Museum, aimed at ages 38. It teaches counting, sorting, measuring, gathering, matching, patterning, sequencing, roleplaying, and sharing. http://www.ocm.org/exhibits_rentals.aspx
 Mathamazing, http://goo.gl/GsAHf, Canaberra, Australia, "24 colourful interactive exhibits that invite visitors to explore how mathematics is part of daily life at work, home and play. Mathamazing communicates the scope of mathematics and the work that mathematicians do, encompassing such topics as topology, probability, architecture and music."
U.S. Museums and other institutions with mathematical content

Math Physics Explore. LaGrange, NY. mathphysicsexplore.org
A new museum of mathematics and physics that recently had its grand opening (July, 2010). 
NY Hall of Science. Queens, NY. nyscience.org
This nearby science museum does not mention math on its home page, but does have two exhibitions with strong mathematical content. The first is the only complete installation of the classic Eames "Mathematica" exhibit, designed in the 1950s. While beautiful, the level of interaction and choice of topics is very limited. Mathematics has blossomed in the last halfcentury into many areas that are very accessible to the general visitor. The second is a collection on "network science" with a number of modern, polished, interactive exhibits which are essentially mathematics, although they are not necessarily identified as such. 
Museum of Science. Boston, NY. mos.org
This museum's only permanent mathematics exhibition is the other surviving copy of the Eames Mathematica exhibit, not quite as complete as the one in the NY Hall of Science. They occasionally have temporary exhibitions with strong mathematical content. 
The Exploratorium. San Francisco, CA. exploratorium.edu
Although the direct mathematical content of this museum is limited, it clearly ranks as one of North America's premier interactive science centers, and it focuses especially on tactile experiences for the visitor. Thus, in many ways it provides an excellent model for an interactive math center to emulate. Moreover, they created the Geometry Playground, which is currently on tour. If anyone has some examples of mathrelated exhibits that are in place at the Exploratorium, it would be great to post them here, perhaps in a comment. 
The MathScience Innovation Center, VA msinnovation.info
This center is directly focused on classroom activities and teacher training, and does not operate as a museum for casual visitors. However, math is one of its focus areas, and they offer roughly half a dozen math programs, in formats including onsite class group visit, lesson kit loaned to instructors, and virtual visit via audio/video connection between the class group and the center. 
A.C. Gilbert's Discovery Village, Salem, OR acgilbert.org
A children's museum set in three historic houses. We mention it here primarily because at one time this museum housed an exhibit called "Midway Math" (developed completely independently from our Math Midway), which can be seen on the fabricator's blog. It is not clear what the fate of that exhibit was, whether it is still on display, in storage, or being shown elsewhere.  San Antonio Virtual and Interactive Geometry center.Â http://www.math.utsa.edu/~fnorman/SAVIG WEB.htm
Webonly Museums AND INTERACTIVE MATH SITES

MathSite: An interactive source for seeing, hearing, doing mathematics. mathsite.math.berkeley.edu
This site has only four exhibits, but current development is active, and is clearly the most thoughtful in terms of clearlydirected online interactive math exhibits of any of the virtual museums listed here. One exhibit, "Dissecting Triangles and Squares," is particularly excellent, in that the interactive puzzles are engaging and satisfying, yet lead you through the proof of the theorem that given any two polygons of the same area, one can be dissected into a finite number of polygons and rearranged to form the other.  Not exactly a museum, but Mathematics Illuminated by the Annenberg Foundation is an excellent interactive web exploration of mathematics.
 VirtualMathMuseum.org

The San Antonio Virtual Museum of Mathematics.
This now apparently defunct project was searching for a physical location to create a dual virtualphysical museum.  The Maths Museum. www.counton.org/museum/outside.html (Hint: click on the front door of the "museum.")
 This is in Russian, but it has outstanding videos: http://www.etudes.ru/
 A Portuguese site with math challenges: http://matematica.overblog.com/pages/englishversion4215974.html
Computer Museums
Although generally speaking computer museums do not emphasize the mathematics of computing, since computers and mathematics are so closely tied, there is some overlap between our math museum concept and existing computer museums. Therefore, we collect links to significant computer museums here.
 Heinz Nixdorf MuseumForum. Paderborn, Germany. hnf.de
 Computer History Museum. Mountain View, CA computerhistory.org
 The Tech Museum of Innovation. San Jose, CA thetech.org