This is a site that uses Google Maps interactive features. While the name points to walking or running you can still use it to make a map for your ride route. The instructions are pretty straight forward. You can even export your route in the GPX format to use with GPS units. Gmap-Pedometer

The site is simple to use. Navigate to a trail or road route you plan to take, zooming down so you get a good level of detail. Click the “Recording” button, then double-click on your starting point. Drag the map around to trace your route, double-clicking at as many points along the trail as you like.

The application tracks cumulative mileage as you pass along the trail or road, and there’s the option of tracking calories burned if you’re running the route. (The latter isn’t particularly accurate, since the application does not take elevation — and thus ascent or descent of the route — into account.)

I found this at PoynterOnline