I liked Geonasis. It was like the Grand Canyon, only much much much much bigger. In an RPG at the KMC Forums my brother plays a Geonasian.
I also liked Kamino. Did you know that the aiwhas (the flying whales) went through several different places? In the OT, the aiwhas were called thrantas and were going to be on Bespin. In the concept art for Alderaan the thrantas appeared again. Then the aiwhas were going to be Gungan mounts, then they switched over to Geonasian mounts. Finally they found their homes on Kamino as flying whales of the stormy planet.