osm on android app

I want to build an android app using osm map\data.
I know its possiable, I just want to know what are the options doing it.
Is there any api I can use?
Futher on I will like to build my own map server using osm data. Is there any one here that did it and can discuss it with me?
Thank you very much

Benetah your crossposting at http://forum.openstreetmap.org/viewtopic.php?id=24897 I can recommend a closer look at the OSM wiki about http://wiki.openstreetmap.org/wiki/Android

Some apps listed there are opensource.

Feel free to investigate further how they display OSM based maps and data.

And about an own tile map server: see http://switch2osm.org