Maybe we can get closer to your aim when you describe what web-sevice or software you already have tried and whetre special features are already present there that you want. And what special feature you are missing in each service that is eventually offered by another service.
Actually I used Google Maps and it is what I need. But it obviously doesn’t run on OSM (and I actually thought that GMaps would be better for my trip until I compared the maps). It also doesn’t allow easily edition after I save the map and has issues with adding new points on the route (it has some kind of point limit after which you need to continue on new map). I tried also bikemap.net but editing, saving and properly displaying saved route seems have some flaws (at some point route began to show start somewhere in the middle of my planned route but the points that were set before that were still visible though not connected with route). What bikemap has that is really helpful for bicycle is the height profile of the route and I haven’t seen this thing anywhere else. Bikemap also has neat function to print route in segments on several sheets of paper so I’d have my route on paper in manageable format on the road. I tried also cloudmade but it doesn’t really satisfy me (mainly due to the fact that it doesn’t allow route refinement by adding points somewhere in the middle on the route, so complicated routes are painful here). I think that sums it.