My mate setup this mapping website recently and I've been helping him look at usability etc. I had some old info on every record shop in Scotland I wanted to update, and figured it'd be a good thing to stick on a map. So I did, and now you can go look at it.
The mapping tool is completely collaborative, so if I've messed up anywhere you can fix it, add new shops I've missed, or let me know if somewhere has closed. If I can pick up some interest I'll set up a new map to do the whole of the UK.