Gamespy provides details and video of John Carmack's presentation at QuakeCon announcing a new game called "Rage".
Rage is a first person perspective game which is a bit of a different direction from their previous titles (Wolf, Doom and Quake). According to Carmack, gameplay-wise, Rage is going to be 50% "run-and-gun" but also with a significant amount of driving action and an adventure component "where you build up your car and add things to it".
Of note, Rage is expected to come as a simultaneous release for Mac, PC, XBox 360 and PS3 and was demoed in parallel at the conference.
Carmack had previewed the same technology on a Mac during the WWDC keynote in June. No release date has been set.