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
Open Office Server Daemon based on older daemon written in python (oood).
Open Office is unstable as a server (memory leaks, not multithreaded, ...), this daemon makes it working in long-term without having to change anything in your code.