HexChat is an easy-to-use graphical IRC chat client for Windows and Unix based on XChat. It allows you to join multiple IRC channels (chat rooms) at the same time, talk publicly, have private one-on-one conversations, transfer files, etc.
Kypeless is a fully decentralised chat and file sharing program. It uses AES-256 encryption for data, Diffie-Hellman for key exchange, and RSA public key cryptography for authentication. It relies on pre-shared public keys.
This Pidgin plugin adds a toolbar to the buddy list to quickly update nickname, personal message, icon, status, and mood. It also allows updating the current song and other parameters, which are updated globally on all accounts that support them.
WeIRCd is a robust, simple, and easy-to-use IRC daemon. Its built-in services make setting up Chanserv, Nickserv, and others very easy. The server supports runtime loaded modules and other modern features.