http://www.sketchup.com/I read about it in the latest issue of Fine Homebuilding, which is a fantastic magazine, by the way. They also have a great site with a message board to ask and answer all sorts of questions:
http://www.taunton.com/finehomebuilding/pages/nmh068.asp?d=True&a=S&s=g&CMP=KNC-GPPC&HBX_OU=50. And they have a sister magazine that actually came first, I think, called Fine Woodworking. My husband has subscribed to both since almost the beginning and he has kept every one of them!
Anyway, the reviewer said that it was a pretty nifty program and while it's no full blown CAD program, it is pretty handy and easy to use. He said don't let the price difference between the free version and the full $495 version fool you, that there really isn't that much difference in the two products (something to do with file saving and sharing capabilities.) The reviewer said it is very easy to use with a very short learning curve.
My husband tried it out a little yesterday and wants to play with it some more.