I was searching around the web for other OS's that I could use for learning purposes and I came across this excellent page by Felipe Martins:
as the URL suggests it is a complete list of vulnerable systems/sites that can be used for studying penetration testing. Top bloke!
There are a number of operating systems and web apps listed that are specifically designed to be insecure so that the beginner/trainee can practice their skills. There are also a number of war games sites that I will have to check out at a later time.
For now I have decided to download DVWA (Damn Vulnerable Web Application) and I was going to go for DVL (Damn Vulnerable Linux) but it looks like they are still working on version 2.0 (to be released soon).