To add to my previous post now that I'm not half asleep, I recommend those videos to anyone who's remotely interested in math (particularly geometry/projections and how things in n-dimensional spaces relate as n changes) or anyone who just likes it when pretty patterns happen on their screen. To someone who already knows a bit about the subject, they may start off a bit slow, but it's worth watching from the beginning just to see how they tie little bits of history into it and how the rather simple ideas at the beginning eventually get extended (in a surprisingly straightforward way) into four dimensions. It's one of the easiest to follow ways I've seen of presenting a very difficult concept, and the projections they use for the four-dimensional objects just look neat (and are a lot easier to make sense of in some ways than the animations on Wikipedia).
