From the Federal Trade Commission. These agencies enforce laws and regulations about the labeling, weight, measure or count of such packaged items as food and household products. These offices also check the accuracy of weighing and measuring devices, for example, supermarket scales, gasoline pumps, taxicab meters and rental car odometers.
Site includes links to agencies online.
From the Consumer Resource Handbook, General Services Administration. Web Sites Better Business Bureau Provides instant access to business and consumer alerts as well as helpful resources. Plus, you can file a complaint online.