One of that great and noble class, the science fiction writers, Clarke was one of my dear companions growing up as a somewhat introverted youth in a small rural community. Not only did the writing of these people - Robert Heinlein, Isaac Asimov, Arthur C Clarke, Orson Scott Card, Ursula Le Guin, and others - give my quirky imagination exciting places to play; they showed me how truly exciting science is, and the reality it exposes.
I am sure I would not be a scientist today without their work. It's conceivable I wouldn't be a Humanist either. Science fiction, with its very personal, human blend of hope, science, imagination, and human narrative, seems to be a quintessentially Humanist endeavour. (Check out this list of SF writers' religious affiliations as evidence.)
I could go on at length, but instead I'll leave you with time to spend reading something of his. Check out the bibliography on his Wikipedia page; read something there that you haven't before (or, if you've read them all, re-read your favorite). Learn about his foundation.
May we all carry on his wake, continuing to realize the dreams he shared with us and always dreaming new ones to draw us into a better and brighter future.