Q is a Cocoa port of QEMU, a free processor emulator.From the site:
Run Windows, Linux and a lot more Systems on your Mac. Q is a feature packed cocoa port of QEMU: Switch fast between guest PCs. Save and restart guest PCs at any stage. Easily exchange Files between Host and Guest. Q makes use of OS X most advanced technologies like openGL, quartz and coreaudio to accelerate your experience with your guest PC. Please remember: At the present state, QEMU is still considered ALPHA software.
I haven't gotten around to trying it out yet as Parallels is serving my needs fine, but it's good to know there's another option out there.http://www.kju-app.org/kju/