Very early betas of NetNewsWire actually embedded an http server. This was before Lite 1.0 shipped.
It handled just one type of request, a request to subscribe to a feed. The idea was that people could put a button on their site that linked to a url like http://127.0.0.1:5335/subscribe?url=http://some... -- and the request would then go to NetNewsWire on your desktop, which would subscribe to the feed. Easy one-click subscribing.
It wasn't my idea -- Radio UserLand was already doing this, and we figured we had to do the same thing.
(But then there was the issue of how to manage two aggregators that want to listen to the same port -- and then more apps that would come along and want to listen on that port too. I decided to remove the http server before it became something to fight over.)
But anyway -- I always thought the idea was interesting, that connection between web page and the desktop. (It doesn't have to be feed-subscribing, of course.)