I think it is obvious that photography can be an art form, just like the practiced placement of pigment on paper or canvas can be an art form, or the manipulation of clay can be an art form. To completely make up a quote: The medium isn't the art, the art is the art.
Still, I heard this question a couple of times at my exhibit opening, so I did a little search and came across some interesting reading, linked below. Enjoy.
Here is a nice statement of the arguments for and against, by photographer Jo Plumridge: "Is Photography an Art Form?"
Michael Prodger of The Guardian weighs in: "Photography: Is It Art?"
Here is an excellent history of the topic, from the Encyclopedia of Art: "Is Photography Art?"
We'll wrap up with another essay titled "Is Photography Art?" This one is by Tom Peck.