I don't know that there are published Pitboss minimum requirements. My guess is that they're paltry though. If you can install Civ IV on your machine, you can host Pitboss.
I doubt that you need to actually be able to
play Civ IV on the machine, since Pitboss doesn't actually start the game itself. It just runs the game files to generate turns and apply the game rules. So I'll bet even if your old laptop has a terrible GPU and isn't too fast anymore, it'll work.
Best advice though is to give it a try... install Civ IV, download and install Pitboss, then start Pitboss. Next, try to connect to the server with your PC. If it all works, download CivStats, post a recruiting thread, and you'll be ready to go!
As far as other places to look for games... I don't really know. CFC has been the best for me, since the Apolyton multiplay forums has turned into the unofficial Diplogame spot.
You can get involved with a Pitboss game called Realpolitik at any time. It's an ongoing game with several players per civ. The game's in progress, but since there are several players per civ you can join right now if you want. The main forums there is:
http://evo-games.net/Home/viewforum.php?f=247&sid=b02c7e71741eebf0a8c185c1d4dda8f9
For more normal games though, the best thing to do is lurk and wait for people to host one, or host yourself. You can post in the various threads here where games are already started and ask to be an alternate, so sometimes players vanish and nobody is playing their civ. In these cases they are given to the first person who asks for them, from what I've seen.