If you are interested in hacking and penetration testing, i am sure you know about backtrack. This operating system is used for penetration testing. Now Backtrack 5 is released and available for download. BackTrack is intended for all audiences from the most savvy security professionals to early newcomers to the information security field. BackTrack promotes a quick and easy way to find and update the largest database of security tools collection to-date.
Our community of users range from skilled penetration testers in the information security field, government entities, information technology, security enthusiasts, and individuals new to the security community.This new revision has been built from scratch, and boasts several major improvements over all our previous releases. Based on Ubuntu Lucid LTS. Kernel 2.6.38, patched with all relevant wireless injection patches. Fully open source and GPL compliant.
Download Here
http://www.backtrack-linux.org/downloads/