If you want to run virtualization software on your Mac machine but can't pony up the money for Parallels or VMware (when it GA's), why not look at the opensource solution from Innotek called VirtualBox.  The opensource virtualization platform is making its way to Mac OS X sometime in Q2 of 2007.  Here is the latest announcement:

"innotek today released a beta version VirtualBox for OS X, bringing its highly successful open source virtualization package to the Apple Macintosh platform. OS X is the third major platform that VirtualBox supports and Mac users can now benefit from the most powerful and best performing virtualization software on the market with the ease of use which Macintosh users have come to expect. VirtualBox for OS X is also the first professional virtualization product that is available free of charge, marking the start of a new era on the the Mac platform. VirtualBox for OS X is based on a beta of the upcoming VirtualBox 1.4 and is expected to be completed in the 2nd quarter of 2007."

Check them out, here.