Wow, that's two in the space of a week.

They say that famous people die in threes.  Last week it was Gary Gygax.  Today, it was Arthur C. Clarke.   He was a great man who predicted the communications satellite, among other things, though he's probably best known for writing 2001:A Space Odyssey.  He wrote more books and stories than I can think of and continued to influence the science-fiction world right up until the end.

Locus Magazine has a more detailed biography.