The most popular site to locate gas prices according to you local zip code is MSN Auto. Just enter your zip code in the site, and you will see the map of your area with gas stations, the highest and the lowest price, and listing of particular gas stations prices in with addresses, starting with the cheapest and going up. The site is updated daily. See screenshot (click to enlarge):
An alternative solution is offered by MapQuest, site, having a significant experience with maps and directions generation. The idea, and the simplicity of getting information is actually the same, but the map is better looking and is easier to use. See screenshot:
Another Web site, specializing in providing gas saving advices is GasBuddy. They claim to use a network of more than 181+ gas price information websites that help you find low gasoline prices. GasBuddy web sites allow motorists to share information about low priced fuel with others as well as target the lowest priced stations to save money when filling up at the pumps. Entering your Zip code, you have several opportunities - to see the prices as listing or as a map. See screenshot:
Webmasters running local sites or specializing on the related topics, might add this interactive, frequently updated map to their Web sites, but to do so, you need to create account on GasBuddy Web site. Without registration, you can embed the small window, that will show Today Local Gas Prices on your site or blog (self updated):
You might find more Web sites, offering similar services, but the three provided seems to be the best on the market. Drive safely, buy cheaply, and enjoy your weekend!