Using OpenStreetMap as source to display Map & Marker(s)

Hi,

Would it be possible to easely use one of the OpenStreetmap source to display OSM maps in webpage and Android App. ?
*as well as letting end users adding few markers from their devices.

I`m in a need for this process in country areas of the world not covered by GoogleMap that is where GM displays only a main road but not all the existing vilages on each side of the road…

Thanks