OpenSUSE is not a good
**general** choice, it is vastly different than most Linux distributions.
The same comment goes for Slackware.
If you want to pick and choose for yourself:
http://livecdlist.com/operating-system/linux
Or try:
(Beginner easy):
http://www.knopper.net/knoppix/index-en.html
or
(More general purpose):
http://www.linuxmint.com/download.html
Note: Some of the developers are using Linux Mint
(with the 'mate' desktop - not that it matters with Linux, you can load any/all desktops and choose between them at login time).
AND: I would recommend that you use them as a "Live CD" (possibly installed to other media) rather than trying to run them in a VM.
(Unless your Mac is one of the PowerPC versions.)