Before I settled on Blender for all my modeling needs I experimented with many different programs including Sketchup. It was owned by Google when I started playing with it, now its owned by Trimble. Some people seem to like it, but it never really worked for me mostly because getting STLs out of it was more trouble than it was worth. But if you are inclined to use Sketchup and are willing to setup STL output the Makerbot group has put together a number of links to help you produce good, clean models ready for 3D printing.
One of the biggest problems with models for 3D printing is that your models need to manifold. "Manifold" easier to define in negatives. If a model has any holes in its geometry it won't be manifold. Additionally sketchup occasionally creates stray polygons that need to be cleaned up. Personally I use Netfabb's cloud service as an all-in-one fix 'em up, but apparently there is a plugin for Sketchup called SuSolid that does this itself.
Actually, now I wish that Blender had a plug in that fixed these problems automatically. Hey! Blender folks, get on that!