From joystiq.com:

Microsoft has just announced that the upcoming Xbox Dashboard update will be hitting Xbox Live on August 11. The update is set to include many new features, including Games on Demand, improved Netflix performance (along with Movie Parties), Avatar Awardables, Avatar Marketplace, the ability to rate games, new Friends list sorting options and more. The announcement also mentions that previously announced Twitter, Facebook and Last.fm support is slated to arrive this fall.
Full Story: joystiq.com