I fully admit to being pretty 2 dimensional, but just stumbled on a new plugin for Sketchup that lets you do all kinds of organic shapes and lumpy models.
I know nothing about it other than from this blog posting, but the gallery has some models in it that I'm surprised could be done in Sketchup. Looks pretty sporty for $39
http://sketchupdate.blogspot.com/2011/03/organic-modeling-with-artisan-plugin.html
Bill