I use Virtual Box on a Mac OS X 10.6.2 MacBook Pro.
Can I create/run a Mac OS X 10.5 guest OS on this setup?
If not, what setup would allow me to run multiple versions of Mac OS X on the same machine?
The only known way to use VirtualBox to make a Mac OS X machine is to use a hacked image known as Deadmoo. Otherwise, there is no "legal" way to do so.