Just downloaded this mileage app from App World. So far it's really easy to use. You can even export your results to an excel spreadsheet!
In case y'all are interested...
I use Fuel Economy which is the best I've tried on my torch.
My only complaint is that it doesn't calculate ppg. I know you see that at the pump but I'd rather have that info for future reference as well as making sure it matches with the pump. I actually picked up a discrepancy before with an app on my old Palm Centro.
