According to the site, the Han Solo project would take the form of an origin story, occurring in the time period between Revenge of the Sith and A New Hope and featuring a younger actor taking on the role of the wisecracking smuggler, with scope for Harrison Ford to reprise his role in some kind of framing device. Meanwhile the Boba Fett movie would take place during the Original Trilogy and see the bounty hunter "at the center of a rogue's gallery of galactic scum". Given the settings, both films would of course allow for the return of popular character such as Chewbacca and Jabba the Hutt - not to mention the Dark Lord of the Sith himself, which is sure to tick a lot of boxes for Disney and Lucasfilm's licensing departments...
At this point in time, it's unclear which of the two projects Kasdan and Kinberg are working on, and there's also no word on any possible directors for either of the spin-offs. Of course, Joe Johnston (Captain America: The First Avenger) is sure to be the favourite for the Boba Fett project, considering his relationship with Lucasfilm (not to mention the fact that he's previously stated his desire to make a feature based on the fan-favourite bounty hunter), while Robert Rodriguez (Sin City: A Dame to Kill For) has recently expressed an interest in tackling a Han Solo movie.
Either way, between these two spin-off features and J.J. Abrams' Star Wars: Episode VII, we should probably expect to be inundated with Star Wars rumours and speculation over the coming weeks and months...