Check out The Math Forum for all sorts of useful information related to mathematics and mathematics education.
Check out the Mathematics WWW Virtual Library to see what is out there on the web.
Here is the Society for Industrial and Applied Mathematics' (SIAM) site dedicated to students
Go here History of Science- lite for information about Greek Mathematics, Ptolemy's Geography, and Greek Astronomy.
Here is the MathArchives website. It has all sorts of information.
The University of Idaho's Mathematics department hosts an Internet Math Challenge. Fun puzzles and free prizes for those who are interested.
You can simulate the infamous Monty Hall problem that has been popularized by Parade Magazine columnist Marilyn Vos Savant. Or go to the Car Talk page and see how Click and Clack handled it (or did not handle it!)
Visit MacTutor History of Mathematics Archive for a comprehensive site dedicated to the history of mathematics. It also provides biographies, an index of famous curves, and a mathematicians of the day calendar. Very useful site to bookmark.
Here is a site dedicated to data sets . "Data! Data! Data! He cried impatiently. I can't make bricks without clay!" ----Sherlock Holmes
Click π to go to something interesting.