I was looking into the client-side aggregation features of eventsites. Unfortunately, eventsites requires FireFox, so I couldn't really play much. I did, however, look into the architecture described in this pair of articles by webkitchen. This clever application uses Google Maps for the event location mapping API, uses Flickr for photos from the event. It uses evdb.com as the background event distributed-database. I actually like the eventful.com site that exposes this database. It is really easy to use and packed with features. I added some venues in my home town, added a couple events and performers and even created some "demands" for shows from bands I really like. Those demand can be exposed on your own site for others to click on and "increase the demand". I like this idea a lot. Maybe Microsoft could use this setup for polling the development community for features we want, instead of this monstrosity.
Anyway, here's my demands for Woven Hand and Over The Rhine showing a couple of styles available. The nicest thing is the way this whole site works to make life easy both for users AND for developers using the API exposed at evdb.com.