Several different federal agencies hold government auctions. The General Services Administration is the granddaddy of them all, because it sells on behalf of other departments. When a federal agency no longer needs something — say, a pickup truck — it reports the truck to GSA, which first offers it to other federal agencies and then to state and local governments or nonprofits. If nobody claims the truck, then the GSA auctions it off to the public, and you get your chance at it.
Additional government sites. There are a few additional sites that can provide tips on government auctions. Guide to Federal Auctions gives a rundown of the various agencies. It provides information about what they sell as well as the departments' websites. GSA supplies information about auction sources. Auctions can be searched by state or auction house
Do your research. Check Kelly Blue Book for the proper price for the vehicle, including its mileage and apparent condition. Always downgrade the condition by one ranking for government auctions. Also, do some smart used-car research, such as checking Consumer Reports for reliability and the frequencies of particular repairs, and checking our road test information if it's a recent model vehicle.