I was going to suggest specific photographers (Eggleston, Saul Leiter, Jeff Wall, etc) who have a good eye for composition, but then I realized that nearly ALL photographers worth their salt are good at composition. The exception to the rule would be some conceptual artists who photograph more out of an idea than visual shapes.
Spend some quality time with the photobook section of your favourite library: pick a stash of books of various genres, eras, tastes, and look at the images. Try to reverse engineer them, and figure out how they are structured.
You can also have a look at Henry Rankin Poore's "Composition in Art" (cheap, Dover) for a couple of tips/recipes to get you started.