I just set my wife up with a copy of NetNewsWire. When I was looking at the preferences, I noticed that NetNewsWire has a feature where the list of the feeds that are subscribed can be shared over Bonjour. This is a pretty neat feature, especially if you are in a location like a conference where there would be a lot of people with a similar interest.
In order to get this to work, the port use for the incoming connections needs to be opened up in the firewall. Port number 30874 needs to be opened to allow this traffic.
Note to Apple: There should be a way for an application developer to add a rule to the built-in firewall. When an application is configured, it should call an API for it to request a port be opened. This would cause the system to present an authentication dialog, where the user could allow or deny the port to be opened.