Source: http://feeds.gawker.com/~r/lifehacker/full/~3/Jz55JTzayx8/gotreception-maps-cellphone-coverage
GotReception is a user driven map of cellphone reception strength. Users can login and submit reviews of the location they are at and the cellphone reception they are recieving there. GotReception then compiles the results of the thousands of user submissiosn into a cloud style map showing the clusters of good reception for the carrier you search for. The sample map in the screenshot above shows coverage for the five major carriers in Detroit. You can look at all of them to get an idea of where they overlap and which have the greatest reach, or par it down to just the carrier you are interested in. For another cellphone coverage tracking service, check out Signal Map.