Certain Xbox Achievements for unannounced games popped up thanks to Xbox360Achievements.org.
Some of these are Halo; Reach, Joy Ride, and Shadow Complex.
The list is currently blank, so were are unsure what exactly the achievements consists of, or when any of these are coming out.
E3 starts today though, and the Microsoft Conference in just a few.
Hopefully we will know more then. Until that occurs, hit the link for more.