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 your primary operating system, booting from a LiveDVD, or using your favorite thumbdrive, BackTrack has been customized down to every package, kernel configuration, script and patch solely for the purpose of the penetration tester.

Official BackTrack 5 R1 change log:

1. This release contains over 120 bug fixes, 30 new tools and 70 tool updates.
2. The kernel was updated to 2.6.39.4 and includes the relevant injection patches.

According to the guys at OffSec, This release is their best one yet! Some pesky issues such as rfkill in VMWare with rtl8187 issues have been fixed, which provides for a much more solid experience with BackTrack.We’ve have Gnome and KDE ISO images for 32 and 64 bit (no arm this release), as well as a VMWare image of a 32 bit Gnome install, with VMWare Tools pre-installed.
We are mighty excited and are already downloading this release just as we speak!
Download Backtrack 5 R1