I consider the Auditor Security Collection the best CD available for the networking professional. The ASC contains almost every network security program (good and bad) known to man. It automatically detects and configures almost all hardware. Output from these programs can be saved to a USB keychain. To top it all off, it's free.
The authors are asking for a small donation (via Paypal) when you download the CD image. Given the hard work that has been put into this software, I would say that a donation is well deserved.
I have admired the open-source community for developing some of the best networking tools available (Ethereal, Kismet, Snort, etc). Traditionally there were two problems with getting the software to work; software installation was difficult and hardware detection (especially with wireless cards) was spotty.
The Auditor Security Collection has solved both problems and in a big way. Auditor is definitely a must-have!