l2mICQ is a Perl-script intended for users switching from Licq to mICQ and vice versa. It pays attention to the flags "visible to user" and "ignore user", and has the ability to only show the difference between both contact lists. This script works for mICQ versions prior to v0.5.
ickle is an ICQ2000 client using the GTK-- graphical toolkit. It aims to bring all the useful features of ICQ2000 to non-Windows users. It supports message/URL/SMS sending/receiving (including SMS delivery reports), status changes, reading away messages, and fetching advanced user info from a server. History browsing and lots of configurability in Settings are available.
Kopete is a flexible and extendable multiple protocol instant messaging system designed as a plugin-based system. All protocols are plugins and allow modular installation, configuration, and usage without the main application knowing anything about the plugin being loaded. The goal of Kopete is to provide users with a standard and easy to use interface between all of their instant messaging systems, but at the same time also providing developers with the ease of writing plugins to support a new protocol. The core Kopete development team provides a handful of plugins that most users can use, in addition to templates for new developers to base a plugin on.
SMSTerm is an application that uses the ICQ2000 protocol to present you a shell on your mobile phone which allows you to interact with your computer from any mobile on a GSM network. It runs a shell on a pty, and allows you to directly send commands to the shell through SMS. Minimal authentication is done over SMS before spawning a shell and offering it to the user on the mobile phone. It is very useful for remote administration tasks, or checking out the status of the network, or just to run some small chores on your system while you are away. It uses Expect.pm in the background. SMSTerm also includes a script to send SMS through the ICQ network from the command line to any GSM mobile, and also includes a PHP script to set up a Web->SMS gateway.
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.