python-jabberbot is a Jabber bot framework for Python that makes it easy to write simple Jabber bots. One can use these Jabber bots to provide information about running systems, to make Web sites interact with Jabber-enabled visitors, or notify the bot owner about updates or changes that are monitored with custom Python scripts.
GNUSTEP Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which is also directly used in Mac OS X as Cocoa). It includes excellent applications for RAD (GORM and ProjectCenter). The CD is available for i486, AMD64, Apple Mac PowerPC, and Sun UltraSPARC computers.
Gizmo Project is a program that uses advanced VoIP technology to allow you to talk with your friends around the world. Gizmo Project uses your Internet connection to make calls to people using other computers. It is simple, and allows you to talk clearly and for as long as you want.
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.
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.
Off-the-Record (OTR) Messaging is a gaim plugin which allows you to have private conversations over the instant messaging system of your choice. It provides encryption, which prevents someone who intercepts your instant messages from reading them; authentication, which ensures that the correspondent is who you think it is; and perfect forward secrecy, which ensures that no previous conversation is compromised if you lose control of your private keys.