I recently started playing with Google's SketchUp, and I think I'm addicted... I've never done any CAD, but this little program (40MB alltogether) is just plain old fun.
There are a bunch of excellent quick tutorials online, and here are some of the more advanced examples this little thingy can do.

I've been playing with it for ample hours, and here's the result (requires SketchUp to view - it's a model of our house, and I think it's pretty much correctly scaled...).

Anyone else been playing with it/interested in doing so?