Google just released Sketchup 7, a tool merely for 3D drawing.
This tool is great to layout 2D backgrounds for the artists to work out or to create models for rendering. The free version does not support DXF and 3DS for export, but it supports collada, which can be read by some renderrers like maya and IMHO autodesk. The Pro version can export DXF and 3DS files.
This tool tries to use 2D techniques to model 3D. You don't have to fiddle around with meshes, nurbs etc (and you can't), instead you do everything by extruding 2D shapes. Have a look at the videos google provides on their site to grasp the concept. It's great for 3D noobs like me ;-)http://sketchup.google.com