The Circle (file system)

The Circle is a peer-to-peer distributed file system written mainly in Python. It is based on the Chord distributed hash table (DHT).
Development on the Circle has ceased in 2004.
Features.
It supports file sharing, instant messaging with buddy lists, the Internet Relay Chat model of sending a message to a channel, and a personalized, trust-based news service.
More unusually, it supports:
Details.
Its DHT implementation is vulnerable to denial of service attacks.
From The Circle homepage:
The Circle currently runs on Linux, BSD, Windows, and Mac OS X.