I know of two good mathematics videos available online, namely:
 Sphere inside out (part I and part II)
 Moebius transformation revealed
Do you know of any other good math videos? Share.
I know of two good mathematics videos available online, namely:
Do you know of any other good math videos? Share. 


I have compiled a list (1500+) of math videos at http://pinterest.com/mathematicsprof/ . If anyone is aware of others, please send them to me. 


77 instructional videos on category theory: http://www.youtube.com/TheCatsters I know you said "only one video per post", but I'm not posting 77 times... 


Most of the talks at MSRI are videotaped and placed on the web here: 


I believe this was mentioned elsewhere, but for completeness, here's Serre on writing. 


My personal alltime favorite is the Klein Four with their song "Simple Finite Subgroup (of order 2)"... it has lots of puns on topology in it, but I guess it doesn't teach anything. 


This video about Andrew Wiles and the proof of Fermat's Last Theorem is the only time I've seen the real excitement of mathematics presented accurately. http://video.google.com/videoplay?docid=8269328330690408516# 


'Not Knot' is also a nice vid 


The Newton institute in Cambridge tapes alot (all?) of it's lectures, and they can be found on the Institutes webpage. High quality for videos of lectures. 


MIT's OpenCourseWare has a few math courses up: http://ocw.mit.edu/OcwWeb/web/courses/av/index.htm#Mathematics 


At the accessible end of the scale, Vi Hart's "doodling in math class" series and subsequent videos are a delight. 


GRASP is a new lecture series at the University of Texas at Austin, which is aimed at bringing some of the fundamental concepts and big picture of the GRASP areas (Geometry, Representation, and Some Physics) to a wider audience (the intended target audience are beginning graduate students). 


The Institute for Advanced Study tapes some of its lectures. They tend to be very good. 


You probably won't learn much actual math from it, but One Geometry is funnier and catchier than a Snoop Dogg parody about 3manifolds has any right to be. 


Along the sphere eversion lines, there is also the energyminimizing sphere eversion constructed by Rob Kusner. I think there is a video of it at http://www.youtube.com/watch?v=I6cgca4Mmcc, though it isn't labelled as such. Rob also has a page at http://new.math.uiuc.edu/laterna/minimax/ with some history of the minimax eversion. 


My personal favorite in Dimensions, that was mentioned before by Gerald Edgar. For a neat and clear exposition the Geom.of 3 manifolds, Poincaré conjecture, etc I recommend this lecture by C.McMullen. Or Das Schöne denken (hosted at the HIM in Bonn), for a good "glimpse in the world of the mathematician". Jos Leys' mathematical imagery contains some (interesting) videos and (a lot of beautiful) images. 


There are Stephen Boyd's lecture videos on convex optimization: 


I guess all of John Conway's lectures are great. Some of those can be found here : http://www.math.princeton.edu/facultypapers/Conway/ 


Not lecture videos or anything, but the stuff from Oliver Labs is very good for just illustrating geometric stuff, like blowups and dual curves. 


The series of videos from IAS School of Mathematics 


Dror BarNatan has begin putting many of his lectures and talks online in video format. I'm not claiming that these are the 'best' online maths videos, but they're certainly interesting, and in particular he's come up with some neat tricks to associate publicly editable annotations with particular moments in the video. 


The IHES also has a lot of online videos. In particular, I like very much the ones from the "Colloque Grothendieck". 


This is an old thread, but this video was recently posted to the Don Davis topology list, and I have to share it. It was created by Niles Johnson at UGA and it illustrates the Hopf fibration. 


This one is quite old but it was fun when I watched a few years ago. It's about Fermat's Last theorem. 


Lots of Lie Theory talks: http://sms.cam.ac.uk/collection/533438?mediaOffset=20&mediaMax=20&mediaOrder=asc&mediaSort=title#Media 


I am surprised that nobody mentioned the fourweek workshop at Göttingen on arithmetic geometry in 2006 summer. Almost all of the videos are still available. Wonderful videos. 


Videos recorded at IMPA: http://video.impa.br/index.php?page=download (some in English, some in Portuguese) 


The "Touching Soap Films" series by Springer. about minimal surfaces. Some excerpts of the video are available here: http://page.mi.fuberlin.de/polthier/video/Touching/Scenes.html 


This video is less about mathematics, but about a fascinating mathematician in two bodies who helped saving medieval unicorns  students liked it. 


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