A new game-for-cash operation has opened up. It's called geePlay.com and it is based in Slovakia.
Basically you open up an account on the site, deposit some money, and start training in the one game they offer, Teeworlds. Once you feel that your skills are passing 'noob' status, you can play the online game in deathmatch and team deathmatch modes against other geeplayers, and if you kill them before they kill you, you win real-life moola.
The Teeworlds game is an open-source, platform side-scrolling shooting game, that has been around for a few years now. It is common FPS-style weapons, like shotguns and rockets. I haven't personally played the game, but it doesn't look like an incredible amount of skill can be used playing it -- the game looks pretty simple.
geePlay.com isn't the first website of its kind to open, offering money-games for online gamers. The most notable cash-game site, tournament.com, closed its doors a while back, and has been "temporary offline" since November of 2007. geePlay currently has a small user-base, but they are relatively new -- it'll be interesting to see if game-for-cash sites ever catch on in a big way.