Marvin is a library (also usable in framework / application form) that makes it simple and fast to build applications around IRC. With an emphasis on making common tasks (e.g. replies, bots using method call style syntax and the like) easy, whilst still making it possible to do more complex thing...

Evented Twitter Library of Doom

A library to enable per user / group authentication on a read / write basis for git repositories running over ssh

A client library for spinderella (http://github.com/Sutto/spinderella)