Quassel IRC is a modern, cross-platform, distributed IRC client, meaning that one (or multiple) client(s) can attach to and detach from a central core -- much like the popular combination of screen and a text-based IRC client such as WeeChat, but graphical. In addition to this uniqe feature, we aim to bring a pleasurable, comfortable chatting experience to all major platforms (including Linux®, Windows®, and MacOS X® as well as Qtopia-based cell phones and PDAs), making communication with your peers not only convenient, but also ubiquitous available.
And the best of all: It's free - as in beer and as in speech, since we distribute Quassel under the GPL, and you are welcome to download and see for yourself!
We are building an Open Source Jabber/XMPP solution. Our goal is to provide a complete environment for basic instant messaging use, stable and easy to extend for all variants of instant communication use cases.
Spark is an Open Source, cross-platform IM client optimized for businesses and organizations. It features built-in support for group chat, telephony integration, and strong security. It also offers a great end-user experience with features like in-line spell checking, group chat room bookmarks, and tabbed conversations.
Combined with the Openfire server, Spark is the easiest and best alternative to using un-secure public IM networks.
RT stands for real time. An online chat application based on rails, very good example for heavy AJAX use. Hasn't published any sources on Rubyforge so far (22nd of Jan 06). Could become a killer app as part of a rails based groupware.