Until recently, runners have had to guess at their running distances or get in the old family station wagon to use the trip odometer to trace the course. The disadvantage of this is that you can't always take your car the same way you run (one-way streets, trails/bikepaths, etc.). There are new popular GPS units for runners that claim to do the job, but these need a clear line of sight to the sky and tend to get confused around tall buildings or under heavy tree cover.

Here's a great new application for Google Maps that allows you to double click your way around any course to determine your total distance.

It works perfectly as far as I can tell.

[HT: Dave Reed]