Not really. Out here in Seattle, the Arco/BP stations have the cheapest gas as a general rule. If you are in a large metro area, you can check out Gas Buddy and/or GPW before you set out.
http://www.gasbuddy.com/
http://www.gaspricewatch.com/new/
And remember, if you keep a grocery price book, you can track gas with it just as well. Then your buying strategy changes a bit. If you see a low price no matter where you are or how low your tank is, buy some.