Tim: I already have a Google email address,
john.c.baez AAATTT gmail.com
where "AAATTT" stands for that little @ thing.
Please let me know what else I to tell you, or do.
Apparently subversion is so simple that even mathematicians use it (to collaborate on papers written in TeX). Alas, I have not personally reached the point of using version control systems for collaborative math projects. But I'm not opposed to it.