There are coupons hidden on Google Maps, but they're super difficult to find. They only appear when you click on a listing that has coupons already loaded. This site helps you to idenfity where coupons are by just finding businesses with coupons.

To try, first just search on a location like "new york" or zip code. This will bring up all coupons near this location. You can also narrow the search afterwards by searching on things like "restaurant" or "thai" or "hotel."

http://www.unclecoupons.com