Sniffing is a program that monitors and analyzes network traffic, its occasionally used for a program that analyze data other than network traffic.
Cain & Abel:
Cain & Abel is a password recovery tool for Microsoft Operating Systems. 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.
Wireshark is the world's foremost network protocol analyzer. Its mostly used for capturing a network packets.
Ettercap is a suite for man in the middle attacks on LAN. It features sniffing of live connections, content filtering on the fly and many other interesting tricks.
You can use Ettercap from Backtrack Or you can download as below