I'm not much of an artist but I came across this tool that looks quite good for 3d modeling. Its comparable to Bryce 3d without the price tag. If anyone tries it, be sure to post your results.
http://www.blender3d.org/
From the site:
Blender, the open source software for 3D modeling, animation, rendering, post-production, interactive creation and playback (see the features and screenshots). Available for Windows, Linux, Irix, Sun Solaris, FreeBSD or Mac OS X under the GNU Public License.