Ted Leung points out Howl, a Zeroconf/Rendezvous implementation for Windows and Linux/BSD:
Now the rest of us who have been hearing about the MacOS X Rendezvous Bonanza have a chance to get in on the action. The folks at Swampwolf have produced howl an open source Rendezvous/ZeroConf library that works on Windows and Linux. They’ve release the source on SourceForge under the BSD license.