phpICQ is a small and nice ICQ client written in PHP with php-gtk.
phpIcqBot is an ICQ bot written in PHP with full plugins (modules) support.
PTL is a PHP library which allows connections to the AIM network via the TOC protocol and is perfect for running chat bots.
ptyaim is a simple curses client for AOL Instant Messenger, ICQ, and IRC. It runs on many Unix-like systems, and Win32.
ICQ clone written entirely in Python. Uses OSCAR AIM protocol instead of native ICQ protocol, as well as icq2000b does. Many GUI frontends supported, but native one is Tkinter-based.
voltMessenger is a web-centered IM system. It consists in a server written in PHP that can run on most webservers, and a client written in C++. Easily deployable in office environments or as a website extension. THIS PROJECT HAS BEEN SHUT DOWN.
wapbber is intended to be a fully featured jabber client for wireless devices, written in Perl, using Wireless Application Protocol (WAP).