Here we go again, this time it's Serious Sam 3. It activates on STEAM. I've confirmed it. Steam has it for $19.99 today.
This time it's from GetGamesGO. Yes it's legit. Yea I've never heard of them either. It looks Eurogamer owns them.
Anyways, buy the game, they accept Paypal as well and they will email the key to you. I got my key in about 5 minutes after ordering.
Just copy and paste that key in to "Activate a product on Steam" in Steam and your done. You can d/l it from Steam, runs in Steam, is as if you bought it from Steam.
US, UK confirmed and probably most of Europe.
Btw, Red Orchestra 2 Heroes of Stalingrad is $11.99 as well from that site. Registers on Steam too if anyone is interested.