This web page is intended as a convenient place to keep short expositions, answers to questions, commentary and discussion, etc. What I put here is often less polished than my publications, and may lack detail. My publications should be regarded as my definitive opinions on their subjects, as of the time they were written, whereas these are just off the cuff remarks.
I've got another page on which I keep notes on recent books.
If you are looking for interesting mathematical discussion on the web other than research papers, then you should take a look at the web pages of John Baez (see also here), Keith Conrad, Noam Elkies, David Eppstein, Lance Fortnow, and Timothy Gowers. (Of course they've all got very interesting research papers online as well.) Some of these sites are fairly sophisticated; Nick Hobson has a great collection of more accessible mathematical puzzles, requiring only a high school mathematics background.
I'm definitely interested in hearing from people who read this (my contact information is on my home page). There are just a few things to keep in mind.