Math java applets has great animated graphics for Geometry through Calculus. These are from Japan. See also updates page for updates and other applets on conics, vectors, and more. Math in Daily Life - Examples of math in daily life. Includes a nice annotated list of Math Web sites .
Students can submit their solutions.
College Problem of the Week Shack's Math Problems - Great problems. Most of these are true web-based learning activities. I especially like BonVoyage . Play interactive NIM . Interactive Mathematics Miscellany and Puzzles - Lots of puzzles with java applets.