Orson Scott Card's Ender series. 6 books. Ender takes computer gaming to a new level...
Anything Heinlien. Read Starship Trooper, which bore only slight resemblence to that piece of crap movie. Read the Moon is a Harsh Mistress and then look at the date. 14 years before you could buy a 4 function hand calculator (for $300).
Robert L. Forward for hard science fiction, using real science. His book "Indistinguishable from Magic" should be read by anyone planning to live beyond 2015.
The cyberpunk stuff, but someone already mentioned them - Gibson, Stephenson, Sterling, and someone already mentioned Phillip K. Dick, Frank Herbert and Gordon Dickson.
Ursala LeGuin. The Dispossessed. The Left Hand of Darkness. "Left Hand" got me thinking seriously about how we regard our sexual roles, and why. Pretty interesting stuff.