There are quite a few website like that. (It's one of the better ones although I've just found some out-of-date information on it).
When I'm working on travel surveys (often on cycle paths 'in the middle of nowhere') I like to know where the nearest large supermarkets are, so that I can find a loo and a coffee during my breaks. This is the site I use for that purpose (although it's got far more information as well):
http://www.cheapmortgages.com/postcodes/