Andy's pick of the week on MacBreak Weekly 397 is a 3D development application called Rhinoceros. It has been a very popular program on Windows, and now the developers are working on a version for Mac. While the app is still under development, it's being offered as a free download.
Even though this isn't a final release, Andy has found it to be very stable. The only limitation right now is the lack of extended plugin support. It's also important to remember that you'll have to upgrade to the newest development build as they are released, since old builds will expire.
Andy has found the interface of Rhino 3D to be clean enough that he didn't need documentation to figure out how to use it. There are plenty of videos online that show what can be done with it, though. Whether you have a real purpose for this kind of application, or if you just want to play around with 3D models, this is a great way to try it out.
To hear Andy's recommendation of Rhino 3D, check out MacBreak Weekly episode 397.