http://www.shodor.org/interactivate/activities/pascal1/index.html Pascal's triangle in various coloring patterns.
http://jcrystal.com/steffenweber/POLYHEDRA/p_05.html Have some fun with Polyhedrons.
http://javascript.internet.com/games/hanoi.html The Tower of Hanoi.
http://mathforum.org/isaac/mathhist.html Famous Problems
http://www.h-schmidt.net/MandelApplet/mandelapplet.html Constructing the Mandelbrot Set
http://www.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html Graphing Projectiles