A few weeks ago I discovered the Walkscore website. You give it an address and it uses Google Maps to plot nearby facilities and calculates a walkability value for the area.
We live near Coventry city centre and putting in our address gives a walkability of 53/100, or 'Somewhat Walkable'. There are some shops nearby which aren't on the map so I might add them and see what difference it makes.
I've re-run the score for our home address and it's gone up to 71/100 which is still 'Somewhat Walkable'. It looks like some of the local shops and take-aways have been added to the database.