When looking for calendaring software I found this:
With Eventful, you canâ€¦ * Discover interesting events, venues, and calendars * Narrow your search by time, place, keyword, proximity, and other criteria * Create unlimited web calendars, with built-in iCalendar, RSS, and web publishing tools * â€¦and it’s all FREE!
Pretty neat, it supports tags and groups, RSS and iCal. It uses an API called evdb, which stands for “events and venues database”. Not exactly what I was looking for, but I figured I’d add it for now and add an update once I’ve had time to look at it.
Update: Apparently, CalendarHub is also pretty nice. No API though.