Gigr.net is a community driven gigs portal built on Ruby on Rails. It already talks to audioscrobbler & itunes (to pick up your listening habits) and exports iCal calendars / RSS feeds with shows involving the bands you're currently listening to. It's heading in the right direction by learning to talk early on. What i mean is that this kind of service gains value by playing well with others and that's precisely what Gigr has set out to do. Solid import/export options already.

Anyone can upload information about shows/artists/venues. Username/email is all that's required to sign up for free. Do it. It's just getting off the ground but there's already a ton of shows in there.

Note: If you're a Rails developer then get talking to Ernest about access to the SVN repository. This is just the kind of service that could wind up embedded in something like the last.fm service.