I'd be inclined to suggest buying photo art/coffee table books -- collections of great photographs. To me exposure to good photography helps to inspire your own, as long as you don't succumb to just imitating. You would expect the Beatles to have listened to The Band, and Michelangelo was probably familiar with the work of Leonardo da Vinci.

Which books to purchase (or online galleries to review) really depends on what kind of photography you are into, but if you don't know of any famous photographers you could try google/wikipedia searches like "contemporary photographers" or "american west photographers" and once you get some names start looking up their work.

Or you could start looking at the work of Ralph Gibson, Edward Weston, Ansel Adams (who was kind of a geek, liked to understand processes, why things worked the way they did), Henri Cartier-Bresson, Richard Avedon, Diane Arbus, Annie Leibovitz, or Gregory Crewdson.