Discovered this interesting website that takes Trackbacks to another level. TopicExchange.
The concept seems to be kind of similar to Usenet newsgroups, but not nearly as many newsgroups at the moment. To post to a topic channel as they're called, you make an entry in your trackback-enabled blog, and ping the URL for the group. Or you can create a new topic channel. Each channel also has an RSS feed, making it easy to keep track of with your favourite RSS aggregator.
A very nifty concept. Shall have to keep track of this one.