Packetyzer is a network protocol analyzer for Windows, also know as a packet sniffer. It is based on the Ethereal project, but provides a native Windows GUI. Packetyzer can capture from virtually any network adapter and supports many advanced features.
Not updated in a long time.
Hey see, today I found the best software - OpenSpammer. Spam all the emails now http://sourceforge.net/projects/openspammer/
excellent tools. Quite useful for network admins