Artcam is one expensive program.
Aspire has some carving tools.
Some basic spirals can be made with Moi, including Euler/Clothoid and other scripts.

I've only tried doing shells. And Acanthus. http://surfacefragments.blogspot.com/2010/04/acanthus.html
There is the 2d work, and the "harder" 2 1/2 or 3d work...

- Brian