Bristol and bike theft seem to be mentioned in the same breath every other day on this forum. I've recently lost one myself and I thought it would be useful if there was one central website that people could report thefts on, and also get updates on any anti-theft initiatives by the police and the authorities.
It's a blog so you can subscribe to it (please do, it'll be much more effective if people get notified every time it's updated), leave comments, or get in touch if you spot someone's half-inched wheels.
Check it out at
http://stolenbristolbikes.blogspot.com/
Shame it's a blog as it's blocked for me and probably for a lot of other people at work.
Top idea though.
I'm a bit of an ingenue when it comes to blogs, but I understand that you can have multiple users adding stuff, and subscribers can get an update every time a new post is added. So it might not be ideal, but it's better than a regular website in some respects.