Q. Is there AutoCAD for Mac?
A. Not really.
Q. Can I run AutoCAD on a Mac?
AutoCAD can't run on Mac OS like the latest Mac Leopard OS X but with the help of the latest Mac OSX that can run on Intel processors and use Boot Camp it's possible. Leopard includes Bootcamp and that way you can run AutoCAD, AutoCAD Architecture, Inventor or other "heavy" Windows applications on your Mac. But still you need to have Windows OS like Windows Vista or Windows XP.
AutoCAD for Mac have existed but is a bit of the history. It was AutoCAD R11 and AutoCAD R12 that was also released for Mac.