open street map
Open street map is the place to be, us Londoners should all use it a bit more as the maps are often much more detailed and cycle/walking friendly.
As much as I love google services, I do prefer the principles of open street map and it has much more potential for doing clever collaborative things.
You can compare the two types of map here: http://tools.geofabrik.de, or use this clever transparancy tool to switch between the two.
