Thought I'd throw in my 2 cents after having researched this a bit. My wife and I are planning a trip around the Alps this summer. I bought a Garmin Edge 800 and started to look into route planning tools. First I bought all the maps I needed. I checked out MapMyRide and BikeMap.net. Both are good for showing rides but not necessarily for routing. Bikeroutetoaster.com and VeloMaps.org (from where you can download OpenCycleMaps and use a route planner like Mapsource) seemed like they would do the trick but in comparing them with a route that we took years ago (Prague - Budapest) they were not routing along known cycling routes. Best I've been able to find so far is OpenRouteService.org and Yournavigation.org. Both interfaces are a bit limited and I'm surprised that they don't show the underlying cycling routes from OpenCycleMaps on which they're based, but they seem to work.