Today's software picks are both free, open-source 3D packages.

Blender

Blender is a free, open source 3D modeling, animation, and rendering application. There are versions for Mac OS X, Windows, and Linux. Here are some of the highlight features:

• Non-overlapping and non-blocking UI delivers unsurpassed workflow.
• A range of 3D object types including polygon meshes, NURBS surfaces, bezier and B-spline curves, metaballs, vector fonts (TrueType, PostScript, OpenType).
• Animation curves/keys, outliner.
• Armature (skeleton) deformation with forward/inverse kinematics, auto skinning and interactive 3D paint for vertex weighting.
• Very fast built-in raytracer
• Oversampling, motion blur, post-production effects, fields.
• Environment maps, halos, lens flares, and fog.
• Toon shading.

There are also a lot of free python scripts that add functionality like import/export capabilities for a variety of formats, though there is no FBX support yet.

As far as learning resources go, check out the free online Wiki Book, Blender 3D: Noob to Pro. It's a great resource that has been put together by the Blender community.

Also of interest there is a short film called Elephant's Dream that has just been released. It was created completely with Blender. It's being distributed over the Internet as the first open source film.

Wings 3D

Wings 3D is strictly a 3D modeling program. It's very minimalistic for those who want a work environment dedicated to modeling. It's still in beta, but is being used by fair sized community nonetheless. One of the thing I like is that it supports OBJ and FBX formats right out of the box.

Wings 3D is available for Mac OS X, Windows, and Linux. The Wings 3D: User Manual is available online as a free Wiki Book.