Recently I went running out of town and could not get my GPS to work for me to know how far I ran. By using Google Maps, I later was able to map out the route and determine how far I actually ran instead of guessing the distance. The days of driving your car to determine that distance of the route is in the past. Further it does not work well where there are one way streets involved. Note a few weeks ago I did a post about Google Maps. I did not include this feature as it deserves its own space.
I used this to measure the distance of a run I already did. You can of course it to plan a path for running, bicycling, walking, etc. It is a tool that can come in handy. However the next time you tell someone that it is a short walk to wherever you want to walk with them to, they can check if it really is a short walk later on.