Other tools

arpspoof, dnsspoof, macof:

permit interception of network traffic.

filesnarf, mailsnarf, msgsnarf, urlsnarf, webspy:

catch interesting informations:

files transfered by NFS v2/v3 with UDP/TCP
be careful about your private keys,

messages transfered by POP/SMTP, IRC/ICQ/AOL/MSN/Yahoo,

visited URL:
in a CLF log file,
live in Netscape.

tcpkill, tcpnice:

facilitate data catching.