of course, that only allows virtualizing solaris, but it works very well for our uses: fast, easy, and free. Mind you, that's in production, where we run strictly headless. On the desktops here, Virtuabox works well here on linux for virtualizing windows so we can test the windows browsers for those things we need to test them for.

This is a Solaris on Sparc in the backroom and linux on the desktop shop here.