Virtual Machines?
 

I'm interested in running backtrack on a virtual machine (or vmware?) what would be a good one to use?

I'm getting it because I need to learn how to use Backtrack and well virtual machines. Its just daunting trying to learn linux OS (ubuntu 8.04) all at one time.

Any sites greatly appreciated.

Ubuntu 8.04 is quite old; it reached end of life a year and a half ago. Why not consider a newer version?

As regards VMs, I have had good experiences with VirtualBox OSE to distro hop many different Linux distros, as well as install Windows XP.

In addition to what frankbell already posted, if you are not a network and security expert then Backtrack is of no use for you. It is a distribution meant for experts, made by experts.