A visualization of the Hopf fibration, very cool video by Niles Johnson 2003, who first learned about it in this very course!   Wikipedia article Informative article that discusses higher dimensional generalizations.
  Four fibers in the Hopf fibration
  How to Fill n-Dimensional Space with Hoops
  Hopf torus A three second MPEG animation that should be played in slow motion.
  The Flat Torus in the Three-Sphere Animations by Tom Banchoff, who has been making computer animations to illustrate geometric ideas since 1970.