I'll be throwing links to articles and descriptions of rating systems for Go, and maybe some other games, in here, as I run into them. I find rating systems morbidly interesting.
And, not at all related, is the problem of tournament pairing algorithms. I'm collecting that because I'm planning on writing a pairing program, because the ones that exist are either non-free (McMahon by Gerlach) or Windows-only (Gotha by Vannier), neither of which is acceptable for me.