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.