DVD INDOOR Projector?

I'm looking for a projector that could be mounted on the ceiling and project onto a screen a couple feet away and slightly below it. (This projector will be going into my room). I'm new to the novelty and so I was wondering if anyone knew of a site that sells them and gives alot of information (I.E: The distance needed, wether or not the distance required is adjustable, the size, DVD compatibility).