Didn't notice these-
Sam Spade - originally designed to track down spammers, many other uses though. Don't know what is going on with the main site.
Cain & Abel - "It allows easy recovery of various kind of passwords by sniffing the network, cracking encrypted passwords using Dictionary, Brute-Force and Cryptanalysis attacks, recording VoIP conversations, decoding scrambled passwords, recovering wireless network keys, revealing password boxes, uncovering cached passwords and analyzing routing protocols."
Nmap - "utility for network exploration or security auditing" must-have.
Ultima Port Scanner & Traceroute - names say it all
Foundstone Network Security - free network/security tools.
OllyDbg - "OllyDbg is a 32-bit assembler level analysing debugger for Microsoft? Windows?. Emphasis on binary code analysis makes it particularly useful in cases where source is unavailable. OllyDbg is a shareware, but you can download and use it for free."
SuperScan - "Powerful TCP port scanner, pinger, resolver."
Zhorn Software -Useful freeware.