The full list of free comics that will be available as well as comics that will be available for purchase at launch is on Dark Horse's website. It should be noted that there are no Star Wars titles currently scheduled to be available at launch.
Dark Horse Editor Randy Stradley commented on the lack of Star Wars titles on the Dark Horse Forums:
The digital store will open in a week or two, but we're still working out details on a deal with Lucasfilm for digital Star Wars on platforms other than the iPhone.Dark Horse is also holding a giveaway for an iPad 2 and $100 in digital store credit if you sign up for their newsletter. Sign up HERE.
SOURCES: Dark Horse and Dark Horse Forums