Military Science Fiction -- The Forever War by Joe Haldeman
Space Opera -- Old Man's War by John Scalzi (although this is more military SF)
Cyberpunk (anything you guys would suggest other than Neuromancer by William Gibson) -- Spin State by Chris Moriarty
Steampunk -- The Steam Magnate by Dana Copithorne (partially because it is really damn good and partially because it's the only book I've ever read that I could call steampunk)
Post-Apocalyptic -- Other than 1984...I don't know...Cell by Stephen King, but that's not a great example, though I liked the book.
Hard Science Fiction -- Foundation by Isaac Asimov
Humorous SF -- Hitchhiker's Guide to the Galaxy by Douglas Adams
Soft SF (or Socio-SF) -- Ender's Game by Orson Scott Card
Dystopian SF -- 1984 by George Orwell
Post-Cyberpunk -- I have no idea...I didn't know there was a Post-Cyberpunk movement until recently...
High Fantasy (other than Tolkien) -- I can't think of a really good example of this other than Tolkien. Some mediocre examples, sure, but nothing really concrete.
Urban Fantasy -- Peeps by Scott Westerfeld (though it's sort of SFish)
Dark Fantasy -- The Book of Lost Things by John Connolly (this is dark YA fantasy actually)
Heroic Fantasy (again, other than Tolkien) -- Shadowfall by James Clemens
Science Fantasy (or Scifantasy) -- Bright of the Sky by Kay Kenyon.