I buy the cheapest priced gas possible, yet I don't waste gas driving around looking for the cheapest prices in town, How? I use the internet whenever possible. Here's a list of sites that monitor gas prices so I know who has the cheapest prices in town. 

gasbuddy. com - is a pretty extensive and comprehensive commercial site with ads.  May be limited by commercial bias.

gaspricewatch. com - is a grassroots site operated by Joe Public "watchers" who report in prices. Limited by number of volunteer "watchers". msn. com - is a national survey by participating retailers who don't necessarily update prices daily.

fueleconomy. gov - go to this site to see local fuel prices in your area. Affiliated with GasBuddy.

fuelgaugereport. com - is operated by AAA and is more for the highway traveler and long haulers.

gaspricealert. com - is a scam e-mail churn site that requires you to "signup" with an offer to get virtually no info.