Xfire Inc - 15.58MB (Freeware)
Xfire is a free tool that automatically keeps track of when and where gamers are playing PC games online and lets their friends join them easily. It works regardless of game type, server browser, or gaming service that a player is using.
Xfire combines instant messaging, a server browser, peer-to-peer file downloads, in-game messaging, screenshot and video capture and one of the most active gaming communities in the world into a small, simple package. Best of all, it's free!