Upcoming.org is a site that allowed people to publish their events, and therefore you could see all the events by location and/or type of event. Yahoo bought the company, relaunched the Upcoming site, and it’s pretty good (functionality wise at least, I’ve not checked the markup).
You can use your Yahoo account, but even without signing in, it knew my location and presented events in my area. (Now I need to see if it will also show windsurfing events anywhere in the country, but I guess that’s an outlier as requirements go!) Hooking into Yahoo’s resources, they’ve improved the location functions and you can even merge your Upcoming and Yahoo accounts (and “old-skool” accounts give you the chance for a free t-shirt).
This is actually a Web 2.0 application (as opposed to having nice shaded graphics and a bit of AJAX), as the more people use it, the better it gets. Macro improving the micro.
Now if only I can find time to go through their API and do something useful with it…