Siemens continues to be the only large CAD vendor with a CAD program to run on all three desktop operating systems. NX 6 runs on Linux, Macintosh, and Windows. The Mac version includes CAD, CAM, assemblies, and drafting.
(The rumor is that Apple funds the development, since Macs are designed with NX. Even if the rumor is not true, NX has a sufficiently expensive price tag that Siemens probably can afford to subsidize development for less-than-monopoly-status operating systems.)
NX 6 for Macintosh is in beta, and is due to ship this summer. It requires a current 64-bit CPU with Mac OS X 10.5.5+.