SNIFFING
Well its Sniffing is a program that monitors and analyzes network traffic to geniune check, its occasionally used for a program that analyze data other than network traffic for pure generate on network.
Cain & Abel Tool :
Cain & Abel is a password recovery tool for Microsoft Operating Systems you Know about that. It really allows easy recovery of various kind of passwords by sniffing the network as you like, cracking encrypted passwords using Dictionary well transform, Brute-Force and Cryptanalysis attacks, recording VoIP conversations its really awesoom, decoding scrambled passwords wow, recovering wireless network keys great, revealing password boxes, uncovering cached passwords and analyzing routing protocol its really Great Tool.
Download : http://www.oxid.it/index.html
Wireshark:
Wireshark is the world foremost network protocol analyzer as i think you know well. Its mostly used for capturing a network packets its really awessom tools for Hacker.
Download : http://www.wireshark.org/download.html
Ettercap:
Ettercap is a suite for man in the middle attacks on LAN its cool tool script kiddie use this tools. It most features sniffing of live connections well, content filtering on the fly and many other interesting tricks to be include.
Download : http://ettercap.sourceforge.net/downloads.html