Sun Virtual Box 3.0I have installed and tested it on my Snow Leopard. It is FREE solution and a very good one. But it lacks behind speed as compared to Paralles and Vmware. I also found some glitches in Share Folders Access.
Parallels Desktop 4.0Parallels Desktop has improved a lot, Before release 381 it was quite buggy, but now it works as smooth, I found its seamless integration "Cohesion" very good better than other two products
Vmware 2.0.5Vmware is fastest of all and it is very good Virtual Solution. Previously I has problems with Share Folders, they were too slow. Now they are blazing fast.
I also recommend to install portable versions of the Application in virtual box to have optimized performance. Presently I am using VMware Fusion 2.0.5.