I've just spent an hour working through the tutorials for Google SketchUp. It's a free 3D-modeling tool. Pretty slick and easy to use.
I worked on 3D graphics and user interaction when I was a Master's student at Brown in the early 90s. What we had then wasn't bad, but the SketchUp UI is easier to use and more functional, and it runs on a regular PC instead of a high-end Unix workstation.
I can see myself using SketchUp to model woodworking projects.