In case playing through Force Unleashed as C-3PO wasn't enough downloadable content for you, you'll be able to go to Tatooine this fall. Assuming you didn't trade in your copy after finishing the game, of course. According to Lucasarts:

The mission begins at the end of the story of The Force Unleashed and re-imagines the Star Wars Saga as if the Secret Apprentice had killed Darth Vader and taken his place at the Emperor's side, becoming the most powerful Sith Lord in the universe. The story picks up as the Emperor sends his new apprentice to the planet Tatooine to dispatch Obi-Wan Kenobi -- who has been hiding on the planet ever since the events of Star Wars: Episode III Revenge of the Sith. During their hunt for the reclusive Jedi, players will also explore the depths of Jabba the Hutt's palace and encounter notorious bounty hunter Boba Fett.

If, however, you did trade in your copy, there will be a re-release of the original game bundled with the DLC, and containing a special Hoth level. Again, from Lucasarts:

The exclusive level concludes the "Infinities" storyline set up in the Tatooine mission, as the Secret Apprentice is sent to the planet Hoth on a crusade to crush the Rebellion once and for all. While on Hoth, players face Luke Skywalker himself while visiting iconic locations seen in Star Wars: Episode V The Empire Strikes Back.

Force Unleashed will also be ported to the PC and published by Aspyr this fall. It is my hope the Secret Apprentice won't spazz out so much when he's using the Force with a mouse and keyboard.