Check out VirtualBox from Sun.
Of course, being a Solaris junkie, I’m excited. This has been out for awhile, but it hasn’t received much press. I’m installing Windows right now on my Solaris machine at work. So far, so good. I don’t care if it’s going to be all that slow, it’ll save me time from dual-booting in the long run. Plus, I can install the various Linux distros I need to work with as well. Very nice!
Oh, yeah, and its free.