I realize I'm opening up a whole can of worms here, but it's always good to incite conversation, yes? Lisa Mikulski at Dragonfly Blu Design has a blog post about whether or not graphic design is art (it is, of course!). I offer this definition of art, which I've always liked:
What is art?
It is the conscious, deliberate production of an event or object of beauty (or emotional import) by a human being, employing not only the skill of the craftsman, but in addition, an element of creativity–original, inventive, instinctive, genius. An art object is an aesthetic artifact, deliberately created.
Art actually lies in the act of creation, not in its result.
–G. Ellis Burcaw, Introduction to Museum Work