BackTrack Linux
"The highest rated and acclaimed Linux security distribution to date. BackTrack is a Linux-based penetration testing arsenal that aids security professionals in the ability to perform assessments in a purely native environment dedicated to hacking. Regardless if you’re making BackTrack you Install BackTrack, boot it from a Live DVD or thumbdrive, the penetration distribution has been customized down to every package, kernel configuration, script and patch solely for the purpose of the penetration tester." Wicked CoOl!