ServerLess TeamWorker makes it possible for a small team (1-10) to work together on a common workplace. An example for this is a distributed issue tracking solution. Clients connect to each other using web services, but work disconnected also.
Naanou is a 'clean-room' implementation of the published Chord protocol from MIT. It is a completely distributed hashtable P2P network, with provable high-performance characteristics.
An open Gnutella network library based on GnucDNA. It is platform-independent, developer-friendly and efficient, developed in portable C++. Easy enough for the casual P2P developer and advanced enough to satisfy the research project needs.