Go to a auto parts store (or Walmart) and buy an inverter. They come in various sizes, plug into your car's power outlet (formerly known as the light socket), and can provide AC power to run your fridge or freezer for a bit, then switch to charging you cell phone, etc. All off your car's engine (suggestion: go fill the tank with gas NOW).

Just don't run the car in a closed garage or similar place...carbon monoxide poisoning ain't fun at all, as I know.