Vernor Vinge

A professor and science fiction author who wrote a lot of influential SF on themes of interest to geeks. Many people know him through two famous short stories: "True Names", which influenced cypherpunks and virtual reality fans, and "The Ungoverned" (based on the ideas of The Machinery of Freedom), which influenced libertarians.

Also the author of The Peace War and Marooned in Realtime (recently collected as Across Realtime). See The Vernor Vinge Project for more details.

He is the first person to articulate the concept of the Singularity, a point in time where current trends in technological and scientific progress/change become so extreme that is impossible to extrapolate what happens past this point. Vernor Vinge generally expects this to occur no sooner than 2015 and no later than 2050. His articles on the web on the subject are quite though provoking.