Rich Corbridge at NewsForge goes over what’s in his toolbox. What’s in yours? I remember when Minicom was my only option for dialing up to my ISP (CAIS before it sucked and the CapAccess freenet before that, in addition to BBSes) in Linux. I used ProComm on the dos/(and later win) side of course.
Ethereal is the hammer in my toolbox. If nothing else works I go for the hammer. It is a full-featured open source sniffer available for *nix and Win32.