I am working in my 11th semester teaching math classes at the University of Michigan. I made web pages for some of my classes. For some reason the main page for Fall 2001 is missing, but some content remains.
This semester I'm taking a class on source coding [EECS 651], which covers material better known as compression. I have a web page with work I have done for the class. I am also taking a math course, Diophantine Approximations [Math 677], which doesn't have a web page. I expect both courses will be very interesting, but I worry that the EECS class will take up too much of my time.
Last semester I took a class on quantum computing [EECS 651] which was very interesting. My other classes, Digital Communications [EECS 554] and Representation Theory [Math 638], did not have web pages.
I've typed up qualifying review solutions to many past exams, mostly in the field of algebra. These may be of some use to those preparing for these exams.
If you have a finite group and you want to find out what the theorems tell us about the number of p-Sylow subgroups then I have exactly what you need.
The Clay Mathematics Institute has offered one million dollars for a complete proof of any one of the seven Millennium Prize Problems.
Eric Weisstein's World of Mathematics is the best resource I know of on the web for a quick outline of mathematical definitions and results.
The Mathematical Atlas offers a visual map of mathematics with very extensive descriptions of the many fields and subfields of mathematics
For some fun there is a huge number mathematical puzzles and proofs at cut-the-knot.org. Many of the problems and proofs make use of java applets, some of which are worth 1000 pictures.