Wikipedia:WikiProject_Mathematics
I've done a lot of wikipedia work before registering. I have a degree in mathematics, but I also have strong interests in sports, mixed martial arts, and piano music. I hope to contribute to all these areas, plus some neglected parts of wikipedia.
I've studied at least a little of most upper-level mathematics, including algebraic geometry, commutative algebra, Lie algebras, elliptic curves, representation theory, algebraic and analytic number theory, complex analysis, computational group theory and number theory, etc. and I've done theoretical computer science and combinatorics. Hopefully this background will be helpful with the math in wikipedia (which is already excellent).