The Penny Arcade Expo (September 4th-6th) and IndieCade (October 1st-10th) are looking for independent games to showcase this year. The deadline for PAX submissions is May 9th, and the deadline for IndieCade submissions is April 30th.
IndieCade entrants are also eligible to appear at the various other expos that IndieCade participates in, including E3 and SIGGRAPH.