(Most of these links are from the GSD blog)
The Dude – a network scanning and mapping software. Free and available for Linux!
SmartSniff – not very interesting, but I found out that you can use raw sockets to sniff traffic (not just to craft arbitrary traffic).
4 Tools You Need To Predict The Death Of Your Hard Drive – good to keep in mind.
From the Lightweight Linux blog: Burn CDs and DVDs with cdw – an ncurses interface to CD burning under linux.