AIM Sniff
http://www.aimsniff.com/

AIM Sniff is a utility for monitoring and archiving AOL Instant Messenger and MSN messages across a network. You can either do a live dump (actively sniff the network) or read a PCAP file and parse the file for IM messages. You also have the option of dumping the information to a MySQL database, a flat file, STDOUT, or any combination of the three. AIM Sniff allows administrators to see how often users are chatting to monitor for abuse and you can also use AIM Sniff to monitor for cases of harassment or pirated software trading. It has been tested on FreeBSD, Linux, and OS X. AIMSniff is developed by Shawn Grimes. This has been added to Privacy Resources Subject Tracer™ Information Blog.