IMIRC is an AOL Instant Messenger to IRC gateway. It connects to an IRC network as an IRC server, so it requires a local ircd to run. IMIRC creates nicknames for AIM users as they sign on, and converts HTML codes, which are used by AIM for formatting, to IRC's control code equivalents. Please note that you must either have your own working IRC server or you must find someone willing to let you link to theirs.
JabberTools is a set of console and Web-based Perl tools depending on Net::Jabber that makes it easier to use Jabber and convert to using Jabber from other instant messaging systems (e.g., AOL and ICQ). The tools include a Jabber account manager and an importer that converts your previous contact lists/rosters/buddy lists into your Jabber roster.
Pedbot is an AOL Instant Messenger robot that features Eliza mode, area code lookup, calculator, dictionary, Google search/spell, IP mapper, password generator, pickup line generator, random quote, random fact, stock quotes, weather, zip to zip distance, and more. Administrative features include wrappers for: ping, nmap, traceroute, dig, whois, w, host, the ability to set configuration hash values through messaging, and initiating conversations with others, manual block / warn commands, and more.
AIM Sniff is a utility for monitoring and archiving AIM and MSN messages across a network. It can be used to monitor for cases of harassment or warez trading. It has the ability to 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 or STDOUT. AIM Sniff will also monitor for an IM login and then perform an SMB lookup on the originating computer in order to match NT Domain names with IM login names (handles).
SDBA Revolution is an open-source architecture written in Perl which simplifies and streamlines the process of writing applications that run on an instant messaging network. It features easy scripting of IM responses, session variables which are consistent across messages, session time limits, support for multiple "apps" from one bot, basic security, the ability to use multiple access lists, and capabilities to allow external application integration. It makes writing IM apps very much like writing mod_perl or PHP pages. It currently supports AIM, MSN, ICQ, YIM, and Jabber. The homepage has full tutorials and documentation.