Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
Packet Peeper - Packet Peeper is a free network protocol analyzer (packet sniffer) for Mac OS X.
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
tcpflow - tcpflow, a TCP Flow Recorder, is a program that captures data transmitted as part of TCP...
NetworkMiner - NetworkMiner is a Network Forensic Analysis Tool (NFAT) for Windows.
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.