POI's along a Route Map
This Google Map mashup lets you find driving directions and will also show you fast food restaurants that you can visit along the route.
The map has some very nice features. There is automatic clustering of the map markers. It is also possible to define the range (in terms of distance along your route) that you wish to see results for. You can adjust the range using the slider control above the map. You can even select the distance off of your route that you are prepared to travel to visit a restaurant.
To top it all you can choose which chains of fast food restaurant that you would like to see results for.