The OpenCycleMap global cycling map is based on data from the OpenStreetMap project. At low zoom levels it is intended for overviews of national cycling networks; at higher zoom levels it should help with planning which streets to cycle on, where you can park your bike and so on.
The map is updated every few days with the latest data from OpenStreetMap. News about OpenCycleMap can be found in the OpenStreetMap archives on my blog.