Bonjour for Windows
Apple has released Bonjour for Windows. Bonjour is the new name for Apple's zero-config technology previously known as Rendezvous:
Bonjour, also known as zero-configuration networking, enables automatic discovery of computers, devices, and services on IP networks. Bonjour uses industry standard IP protocols to allow devices to automatically discover each other without the need to enter IP addresses or configure DNS servers.
Apple also provides and SDK for developers to incorporate Bonjour technology into their applications.