Math Overflow

Because I'd have to forfeit my math blogger card otherwise: you should know about Math Overflow This is a site where people can ask mathematics questions -- the level is basically that of questions which would be of interest to professional mathematicians. I'm rather enjoying it; it's procrastination and education at the same time!

It is also useful for asking questions and being told that I already answered them on this blog.

Evidence that mathematicians have a big Internet presence

If you google genealogy, the first hit is The mathematics genealogy project. In some sense, according to "the Internet", mathematical genealogy is more important than real genealogy! (I have a feeling that the biological parents of mathematicians would be offended by this, so I won't tell my parents.)

If you google AMS, the first hit is the American Mathematical Society. (Societies of meteorologists, musicologists, Montessori schools, etc. show up further down the list.) I have a musicologist friend that I joke with this about, claiming that the mathematical society is the real AMS.

I suspect this is because mathematicians found the Internet early, and seem to be more likely to have personal web pages than even most other academics.

Edit, 4:18 pm: In a comment by Boris, I'm reminded that Google personalizes search results, so what I've said is not true.