SmartSniff for Mac

Cocoa Packet Analyzer is a native Mac OS X implementation of a network protocol analyzer. CPA supports the industry-standard PCAP packet capture format for reading and writing packet trace files.

Wireshark is the world's foremost network protocol analyzer, and is the de facto (and often de jure) standard across many industries and educational institutions.

Ettercap is a comprehensive suite for man in the middle attacks. It features sniffing of live connections, content filtering on the fly and many other interesting tricks.

AirGrab Network Packet Analyzer is a professional network analyzer (also known as protocol analyzer and packet sniffer), AirGrab Network Packet Analyzer performs real-time packet capturing, network monitoring, advanced protocol analyzing...

Packet Peeper is a network protocol analyzer (or "packet sniffer"). Its features include TCP stream reassembly, privilege separation, simultaneous capture sessions, filters, Python plugins, and support for pcap capture files.

NetDumper is a Mac OS X network packet sniffer that dumps all packets to a file. This application is simple and plain, without the overhead of any analyzer.

miruo is a TCP/IP session monitor (packet capture tool). The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks.

Eavesdrop is a free TCP packet sniffer for the Mac. The app allows you to capture traffic on your home network. It is not a very advanced application at this time, and it has some limitations, but it still is a nice app...