"Hard SF," often written by scientists or writers with technical backgrounds, is most firmly based in science and technology and is can be read as a kind of speculative futurism.  Some "cyberpunk" writing, a genre well represented by Neal Stephenson or William Gibson, also seems remarkably prescient in view of current developments in computer and Internet technology. 

There are literally thousands of sites on the web devoted to science fiction.  A Google search on the words "science fiction" brings up about 165,000 listings.  I've selected a few that speak specifically to the predictive value of science fiction.  Several describe the science fiction roots of current technology.  But there are also well-informed skeptics, including Bruce Sterling, who remind us of the many sci-fi predictions that have not been realized.