Map Your Wi-Fi - Free

Makes a map of Wi-Fi access points as you walk around.

Formerly Wi-Fi Map Maker.

Makes a map of Wi-Fi access points as you walk around.

* Maps out the actual coverage of each access point (AP)!

* AP names are displayed on the map

* See street address and area of APs

* You can select the criteria for inclusion on your map

Free version: ads, only 100 APs

Tip:

Looks like this feature of Google Maps will be useful

http://googleblog.blogspot.com/2011/07/download-map-area-added-to-labs-in.html