LiveCDs are the coolest things since microbrews. (Funny how certain “innovative” proprietary software companies never manage to come up with neat stuff like this.) The latest entry in my Cool LiveCDs List is BeleniX, which is OpenSolaris + KDE and XFCE. Solaris can be a bit of a booger to install. BeleniX lets you try it out without installing it to a hard drive, and it also comes with a nice utility for a hard drive installation. Solaris has a lot of advanced stuff you don’t find anywhere else, like DTrace and the ZFS filesystem.
This here article which I wrote my own self, and now shamelessly tout, has some good links for getting up and running:
Tip of the Trade: BeleniX