I sleep on my back, when I can...I can sleep in any position prettymuch, or in any situation, but I usually just lie on my back, when possible.
Actually, some people make fun of me for the way I sleep. I'll lie on my back, with my body straight, and cross my ankles and fold my hands over my chest. And I won't move when I sleep...I'll wake up in the exact same position I fell asleep in.