A couple of General Questions

[Fantomen]

I forgot to mention the Something awful community, they have a large and active group of dom3 player as well, and their own irc channel.

As for how to sign up for a game, it should be evident from the thread title if the game is recruiting, and the first post should state any special requirements as well as the type of server ( pbem or DC ), any further detailed questions you should ask the admin of that game.