Here is an interesting idea: ESF is an XML standard for publishing event information. It’s built off of the RSS 2.0 standard, with the goal of making event data standard.
Fields include the start and end date of an event, the URL for registration, room, URL for directions, speaker information, and audience information.
With data like this a search engine could be created that scoured the web for events and organized them by any of the fields. Very neat idea, I’ll be watching this one.