VERY cool, although based on Linux Red Hat (not that I'm a religious guy, or anything like that).
The page cites these benefits, and it's a free download:
Welcome to the Network Security Toolkit (NST). This bootable ISO CD is based on Red Hat Linux 9. The toolkit was designed to provide easy access to best-of-breed Open Source Network Security Applications and should run on most x86 platforms.
The main intent of developing this toolkit was to provide the network security administrator with a comprehensive set of Open Source Network Security Tools. The majority of tools published in the article: Top 75 Security Tools by insecure.org are available in the toolkit.
What we find rather fascinating with NST is that we can transform most x86 systems (Pentium II and above) into a system designed for network traffic analysis, intrusion detection, network packet generation, wireless network monitoring, a virtual system service server, or a sophisticated network/host scanner. This can all be done without disturbing or modifying any underlying sub-system disk. NST can be up and running on a typical x86 notebook in less than a minute by just rebooting with the NST ISO CD. The notebook's hard disk will not be altered in any way.
NST also makes a excellent toolkit to help one with all sorts of crash recovery troubleshooting scenarios and situations.
Source code is available as a separate download. I haven't tested all these claims yet, but it looks like a good thing to have around.