I read about map my run and tried it. There was a lot of registering involved and the UI over Google maps seemed to move the map around too much as I moved the cursor to do a route.

I mentioned the site to a friend and she suggested Gmaps Pedometer. This site is much simpler: you plot a route, save it and it returns a URL. Just the simplicity I need to find out how far I walked my dog or to lay out a 5k lunchtime jog.