tcpdump - tcpdump is a common packet analyzer that runs under the command line.
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.
SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
NetMonster - NetMonster is a networking app by Michal Mrocek that comes up with features to enable you to get detailed information about your current network right on your mobile phone screen.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.