I used to have a PDA where I’d input my gas mileage every time I filled up. I liked seeing my gas mileage over time with the handy graph. But I stopped using the PDA and even though I still check my gas mileage, I don’t track it anywhere.
FuelFrog allows anyone with a web browser to do the same thing. Not only does it track your gas mileage, it also tracks the price of gas. Twitterers will be pleased to know you can even use Twitter to post updates.