Based on the EA Imagine 2005 Presentation Video, these are the maps for the X-Box:
I would bet that all these are in the PC version too. Though I noticed that Bespin and RhenVar were missing completely from the X-Box demonstration, and they only had 1 map for each of the listed sites. The PC version will have Bespin Platforms and Cloud City, RhenVar Citadel and Harbor, 2 Yavin maps, 2 Kashyyyk maps, 2 Naboo maps, 3 Tatooine maps (including Jabba's Palace) and probably 3 more space maps than the X-Box demonstration showed (for a total of 9).
That brings the total to 35 maps...That should definitely keep us all busy for awhile!