As you probably already know there are loads out there. I am relatively new to Linux and started with Ubuntu which showed me just how good Linux is and how expensive Windows is.
I have tried Knoppix via VMware and I liked it but it doesn't seem to be a very big Distro and is German based (has English dictionary but help for it feels slightly limited.)
PCLinuxOS seems to be a good one yet to install but will when I get a CD-r.
I am downloading OpenSuse as I speak. It will be done at 6 tonight.