Tripcatcher is a free online mileage logger using Google Maps that should prove a great help in submitting your expenses. The application helps you keep an accurate record of your business miles which can save you money on your tax returns.
When you take a business trip Tripcatcher can calculate the distance travelled using the Google Maps API. Tripcatcher can then save the details of the trip, the mileage and other expenses for parking or tolls. If you are making multiple journeys over the same route Tripcatcher can quickly save the details for the added dates without you having yo re-enter all the details.
Currently the map is restricted to UK use because the developers are unsure about the tax rules for other countries.