You can message and share files inside your intranet without a server.
A free course management system (CMS) to create online learning sites
MSHV Amateur Radio Software
Psi+ Project — development branch of Psi XMPP client
Development toolkit for Web Services and XML data bindings for C & C++
Fast Bayesian spam filter along lines suggested by Paul Graham
Showing The Amateur radio Repeaters Tool
Browse on Tor/i2p, Anon p2p Chat / FileTx, Conf / Video VoIP
A lightweight, high-performance Internet Relay Chat server
Cluster wide IPC providing datagram, connection, and bus messaging
an ethernet-based file system for DOS
Transfer disks and disk images between the Apple II and the real world
C library for sending e-mail (with attachments) from C/C++
Open source BBS doors and utilities
The Fast Echomail Processor/tosser, for Fidonet Technology Networks
RSS/Atom/OPML reader in Javascript + CORS proxy in Java
The full codebase of Feisty Meow® Concerns Ltd.