Yep, that Blender.
But it's not really a CAD program per-say, at least not what we are used too. It's more a modeler for CG, animation, effects and stuff like that. So you won't be making drawings or cut-files with it like you can with Inventor or SW, but it's pretty cool if you ask me.
I've been using/learning it for about a month now and it's a totally different beast to get used to, not really hard, just different. The way I started was by watching some video tutorials (there's a ton of them) to get a feel for it before I actually started using it, and that seemed to help.
Hey, for free, how can you go wrong, right?
Anyway, here's a couple links if you want to check out some tutorials.
Plus there's a lot more on YouTube too.
And the latest version of Blender 2.62 HERE
Also a little update on the Paddle boat Perry, here's a couple pics.