The Sculpt Mode in Blender has been upgraded pretty significantly for 2.5!
To celebrate, I've uploaded some .blend files which are already set up for sculpting. There'll be a tutorial on the Thingiverse Blog later, but if you've used Blender to do a few things like model scaling, opening one of these in 2.5 should be mostly self-explanatory.
The different files represent different shapes to use as start points. They all have flat bottoms and so they'll at least start out printable!