I'm sure a lot of iDevice users know this cool trick, but I'm going to post about it so others know about it too.
Let's say you are in a building and for some reason want to know the address. Nobody you would bother to talk to knows it. Luckily, you have an iDevice that is location-aware.
Assuming your device has a good enough fix on your location and is connected to the Internet, just pull out your device, open Maps and tap the blue dot that represents your location. The estimated address will pop up in the bubble that appears.
Note that you should not rely on this. At home, my phone has been known to think my address is my neighbor's address.