NiMC provides an Instant Messaging server and client that runs on a custom protocol that is implemented in python. The project was written as a learning experiment by its author, to get experience with TCP/IP. Great example of how to do TCP/IP wrong
Messy is a collaboration tool for distributed teams. It provides for instant messaging between members of the collaborating groups, a basic group management framework over which additional capabilities can be layered, and a sample concurrent editor.