3D programs for Macs

Perhaps Maya is not for beginners... but I was someone who had not TOO much experience, and found Maya to work fine for me. There are several good books to help you learn it. Though complex, (it takes a lot of thinking, something many people aren't accostomed to) it IS rather intuitive.
Though it goes against what others have said, I recommend getting the $500 student version. But first, try the trial version. It can be obtained from apple for free, the only limitation being a watermark on all renders.