The idea of using geostationary satellites and satellite communication was thought of by Herman Potocnik in the late 1920's, and the concept of geostationary satellites originated with Konstantin Tsiolkovsky.
Arthur C. Clarke wrote an article popularizing the concept as a great way for broadcasting and telecom relay.
The same goes for space elevators, again a concept originating with Konstantin Tsiolkovksy.
Arthur C. Clarke's great contributions lie not with those discoveries, but with the fact that he popularized science and inspired generations of people. No doubt with the sad news of his passing, the media will propagate myths about him that will do a disservice to the truth and in the long run to Arthur C. Clarke himself. Arthur C. Clarke deserves great credit and respect for popularizing Geostationary satellites and space elevators, as well as sparking people's imagination with his stories. There is no need to spread myths about him when the truth is just as great. The more these myths about what he invented are spread around the worse it will be as people find out truth. I have seen him in Sri Lanka on a couple of occasions, and I'm sad that he died and I hope that he is remembered for his work. The world has lost a great contributor and will miss him.