www.tournament.com has CC:S, HL2 and DoD:S
and
www.skillground.com has its own, free, FPS's, racer and beat-em-up
Eurogamer.net had an artical on these not to long back looks alright if your good enough to win matchs you could make a bit of dosh.
Keep a weather eye out for uVme (soon you won't be able to miss it!). This new games site will mean you can earn from your skills - and from those of others. It will feature mainly short (quick play) games of skill though - so may not be what you are looking for. Still in pre-launch but you can find details at http://www.win2win.org - read the Insiders Report and check out the videos.
ps - great questions, shows where the future's at!