There's a new CncSimulator in the works, and by the looks of this preview video, it's a pretty impressive piece of software for hobbyists, or anyone who's ever laid hands on a CNC milling machine or taken shop class.
You can arrange your project in basically any configuration, with any tools you want, like ball mills, drills and disk cutters. Basically, you have the run of a whole workshop's worth of tools to operate and observe however you want. It's like the coolest wood shop field trip ever jammed into your computer.
CncSimulator is "returnware", meaning you can go try it out for free as long as you return to the site every once in a while -- which is a pretty peachy deal, if you ask me. [CncSimulator via Mike Senese]