Overdose is a simple Yahoo! Chat client written in C, and using the curses library for text I/O. It is multithreaded using pthreads, and works on Linux/BSD/Unix and Windows.
This daemon provides a bootstrapping solution to allow p2p servlets to connect to existing p2p networks. The GWebCache and UHC protocols are implemented. It was designed for the GNU/Linux platform, is written in C, and uses the pthreads library.
SuperVixen is an IRC bouncer written in C, and uses pthreads to manage connections (from clients and to IRC server). It's pretty basic and allowes you to have several clients connected to the bouncer at the same time.