Galina Weinstein has a rather nice article uploaded on arXiv recently on the history of the "light quanta" per Einstein's 1905 paper. In particular, she explored why this issue, or rather, the "light complex" that Einstein mentioned in his photoelectric effect paper, was never included directly in his Special Relativity paper. Rather, there was an implication that SR's validity actually depends on the correctness of the photoelectric effect paper and the energy of the light quanta.
Note that in the article, Einstein clearly considered that it is the idea of the light quanta, and NOT Special Relativity, that was truly revolutionary. He thought that Special Relativity was simply an extension of classical electromagnetism.. This is the view that John Ridgen has also taken in proclaiming that it is the photoelectric effect that is a truly revolutionary idea, more so than Relativity (link requires free registration).