Blender.

You mention this word to most artists, and they will cringe, and pass it off as a pile of crap. Yeah, its not as 'good' as Maya. However, its completely free, and Maya is not! Personally I prefer it, but I'm not an artist - I'm a programmer. However, I've been using Blender for there about 5 years now, and have memorised most of the tricky key combinations, can animate, rig, UV map, setup hierarchies, basically everything I *need* to be able to do to throw together simple test assets. My only gripe is the exporters - theres a few, but none of them work how I need them too. If the Collada 1.4 exporter worked well enough that'd solve my problem with the hierarchy I'm currently having. Currently putting together a test bike, properly setup as individual components to tie into physics for Freecross Frenzy. The bike is modelled whilst referencing pictures of real components used to build dirt jump mountain bikes, its *mostly* in correct scale, but I can tweak it later. Anyways, my attempt at being an artist so far: