Couldn't see an existing thread on this.
Seems the long gestating Aliens: Colonial Marines by Gearbox is finally getting a full blown unveiling at this year's E3:
A teaser has been released, along with a release window - Spring 2012. The game will be demoed at E3.
Not much to see in the teaser, but the setup is apparently you play as one of a group of Marines that boards the U.S.S. Sulaco after the events of Alien 3. Presumably it will explore why Ripley, Newt, Hicks and Bishop (hibernating in their cryo beds at the end of Aliens) were ejected from the ship at the start of Alien 3. There is also going to be a trip to LV-426 (which the Sulaco is apparently in orbit around) and the colony of Hadley's Hope, which the teaser briefly depicts. I find that a bit odd given that it was nuked in Aliens, but I guess we'll see how it turns out in due course.
Also, it sounds like the play style is essentially Borderlands in space, with a focus on drop-in/drop-out 4 player co-op.