Bonjour

Description

Homepage	http://www.apple.com/support/bonjour/
Type	Proprietary; portions under the Apache license
Interoperability	None

Formerly known as "Rendezvous", Bonjour is a local-network service that uses XMPP for chat. Unlike most services, you don't need to sign up anywhere to use Bonjour messaging; you only need a local network.