MIT Kresge Chapel, Eero Saarinen, 1955

Eero Saarinen's design for the altar space of the Kresge Chapel at MIT is one of the most sublime pieces of church architecture anywhere, I think, and goes to show that even if you don't like the entire building (I've never liked the chapel's exterior, though it is very much of its time)  there is still much that can be learned. 

The basic ingredients are an oculus (even if you don't have a sky light you can use a appropriate light fixture) artwork that appears suspended in space (the full length metal structure is by Henry Bertoia), and an altar, elevated so that is appears almost to be lifting off the floor, which is why people often compare this assembly to Star Trek.  But I think it's beautiful, and an accessible design for any church to learn from.