How many times have you used an online Map service and wanted to slightly tweak the route (e.g. use a different highway or interstate, or take the south route versus the north route)? Its not easy! You had to give the service an intermediate waypoint to fake it out, then map from the new waypoint to the final destination. Kind of a pain in the butt.
I was playing on Google Maps this morning (yeah, I do it sometimes) and accidentally found a new feature. When your cursor is moved over a driving directions route, the cursor changes to a box. You can then drag the route to a new route! It essentially creates a destination on that new route that the map service thinks you want to drive through. If you right click and remove the destination, the route is moved back to the "google preferred" route.
Here is a quick example for driving to Toledo from Indy. We normally drive through Ft. Wayne, but by dragging the route to somewhere near Richmond (or anywhere along I-70), a destination is dropped in and the route changes.
I thought it was cool. Give it a try!