The Mathematical Quotation Server is chock full of quotes about mathematics. You can even search for quotations about particular subjects or including key words. The mathematics section of the Cornell Math and Science Gateway has links to many other interesting mathematics sites. The MacTutor History of Mathematics Archive . The Geometry Center has information about all sorts of geometry and lots of interesting pictures to look at.
Some curricular material is also available.
There is another site where you can rotate a hypercube , a four dimensional analogue of a cube. If you can read German, you might be interested in reading about Alice's travels in 4D . For basic information about cryptology, visit either the RSA Laboratory's site or the CryptoWeb site. You can also look at an interesting time line about the history of cryptology. If you are interested in thinking more about infinity, be sure to read the delightful story about the Hotel Infinity .