I have no particular standing to speak -- I met him only twice for interviews, once in the early 1980s at Apple, when it had the logo at right, and again in the late 1980s at NeXT -- but wanted to register what surprisingly sad news this is. My sympathies and best wishes to his wife and children.
To what everyone else will say about Steve Jobs's influence on design, technology, and business, I'll add only two things. One, I imagine that people all around the world are struck by this loss. Of Americans in his era, he is one of a handful who had the greatest and most visible effect on people he had never met in countries he had never visited. I think he is recognized worldwide for his individual traits, and for the particular Apple corporate culture -- but also as quite distinctly an American. Biological son of a Syrian immigrant, raised by adoptive parents, college dropout (Reed!), serial re-inventer of his businesses and himself. He could not have done what he did if he were any different person, and he could not have done it anywhere else.
Second, his Stanford Commencement speech, featured now in our Video channel and shown after the jump, is among the few of that genre that bear listening to long after original delivery. Its last part is poignant now, but it all contains things I would want graduates to hear, and to remember myself.