XFire (a free gaming chat application) can be used from within DirectX games. It messes with some games' keystroke manager, but I used to use it from within fullscreen WoW.
I haven't used it in a while, but should work for you. It also tracks how long you play certain games, which map / server you're playing on (for Counterstrike and such), and lets your friends know if you're off playing another game.
It's sweet
XFire got bought by Microsoft for XBox Live integration. Like I said, I haven't used it in a while, so things may have changed.
D