Interesting and promising technologies, links, etc.

PascalWAirplayer - A Python based library
Play2Wifi - An AirPlay server also in Python
Totem Plugin AirPlay - Plugin enabling AirPlay video playback in the Totem media player (Python)
elcuervo/airplay - Airplay bindings to Ruby
Airstream Media Player - C# based AirPlay screen for windows and AirPlay server source code
xmms2-plugin-airplay - Debian AirPlay library
AirPlay NMW - AirPlay plugin for Network Media Tank written in C
AirMac - Turns you Macintosh into an Airplay receiver (Objective C)
AP4J - Java AirPlay video client ### Applications
Beamer - Send any video to an AppleTV
AirParrot - Send the screen of your Mac to an AppleTV (AirPlay Mirroring)
AirServer - The best app for turning your Mac into an AirPlay screen.
Reflection - Turn your Mac into an AirPlay screen.
Banana TV - Another app to turn your Mac into and AirPlay screen
Erica's Air Play Utilities - A collection of Mac utilities for streaming video and photos (not open source)
doubleTwist AirSync - Stream music/videos from your Android phone over AirPlay ### Websites
Stream DVDs - Stream DVD's from a Mac using Erica's AirFlick and VLC
Stream Desktop - Stream your Mac's desktop using Erica's AirFlick and VLC (Audio not supported due to limitations in VLC)
lifehacker - Make your entire home AirPlay compatible