BackTrack is the result of merging the two innovative penetration testing live linux distributions Auditor and Whax. Backtrack provides a thorough pentesting environment which is bootable via CD, USB or the network (PXE). The tools are arranged in an intuitive manner, and cover most of the attack vectors. Complex environments are simplified, such as automatic Kismet configuration, one click Snort setup, precompiled Metasploit lorcon modules, etc. BackTrack has been dubbed the #1 Security Live CD by Insecure.org, and #36 overall.

Personally the only thing ive used BT3 for is to crack WEP. It has alot more functionality and alot more tools inside. Its an excellent linux O/S and can be used for alot more then just cracking WEP.

www.remote-exploit.org for the new Backtrack 4
Well worth a look if you want to crack the neighbours WEP encryption

I'll check it out in the next couple of days, expect a review from me and my neighbour hehe...