Tartarus provides a nice wrapper around basic Unix tools such as tar, find and curl (well, that's not that basic) to provide a seamless backup solution, aimed at automatic gathering and backup. It has the ability to do full as well as incremental backups
13,250 server blades, 75,000 cpu cores, and 112.5 terabytes of blade RAM
This project is an implementation of FTP server in pure Ruby. It features the ability to start a FTP server and publish there any content you want. You are not limited to publish file system subtrees. All FTP hierarchy is dynamic and under your control.
Openfire is a real time collaboration (RTC) server licensed under the Open Source GPL.
Prosody is an exciting new server for Jabber/XMPP written in Lua. It aims to be easy to use, and light on resources. For developers it aims to give a flexible system on which to rapidly develop added functionality, or prototype new protocols.
Prairie is a lightweight OpenID based Internet identity server.