Here's an updated list of what's been nominated so far. I know this isn't my thread, but thanks, everyone, for taking the time.
Anyone is welcome to vote for must-read sf and fantasy, and nominate anything they think deserving.
Douglas Adams, The Hitch-Hiker's Guide to the Galaxy
Douglas Adams, The Hitch-Hiker's Guide (series)
Isaac Asimov, Foundation
Isaac Asimov, Foundation (series)
Isaac Asimov, I, Robot
Isaac Asimov, Robot (series)
Robert Asprin, Thieves' World
Margaret Atwood, Oryx and Crake
Margaret Atwood, The Year of the Flood
L. Frank Baum, The Wonderful Wizard of Oz
Ray Bradbury, Fahrenheit 451
Ray Bradbury, The Golden Apples of the Sun
Ray Bradbury, The Martian Chronicles
Ray Bradbury, Something Wicked This Way Comes
Edgar Rice Burroughs, The Land That Time Forgot
Edgar Rice Burroughs, Martian (series)
Edgar Rice Burroughs, Pellucidar
Jim Butcher, Dresden Files (series)
Octavia E. Butler, Dawn
Octavia E. Butler, Wild Seed
Orson Scott Card, Ender's Game
Lewis Carroll, Alice's Adventures in Wonderland
C.J. Cherryh, The Chronicles of Morgaine
C.J. Cherryh, Downbelow Station
Arthur C. Clarke, Childhood's End
Arthur C. Clarke, 2001: A Space Odyssey
Michael Crichton, Jurassic Park
John Crowley, Aegypt (series)
John Crowley, Little, Big
L. Sprague de Camp, The Goblin Tower
Philip K. Dick, Do Androids Dream of Electric Sheep?
Philip K. Dick, The Man in the High Castle
Philip K. Dick, Radio Free Albemuth
Philip K. Dick, A Scanner Darkly
Philip K. Dick, The Three Stigmata of Palmer Eldritch
Philip K. Dick, The Transmigration of Timothy Archer
Philip K. Dick, VALIS
Charles Dickens, A Christmas Carol
Stephen R. Donaldson, Lord Foul's Bane
Arthur Conan Doyle, The Lost World
David Drake, Lord of the Isles (series)
Harlan Ellison, Dangerous Visions
Harlan Ellison, Deathbird Stories
Carol Emshwiller, The Mount
Philip José Farmer, To Your Scattered Bodies Go
Raymond Feist, Faerie Tale
Alan Dean Foster, Icerigger
Neil Gaiman, American Gods
Neil Gaiman, Sandman
William Gibson, Neuromancer
Tom Godwin, The Survivors
William Goldman, The Princess Bride
Phyllid Gotlieb, Sunburst
Joe Haldeman, The Forever War
Peter F. Hamilton, The Night's Dawn Trilogy
Robert Heinlein, The Moon is a Harsh Mistress
Robert Heinlein, Starship Troopers
Robert Heinlein, Stranger In a Strange Land
Robert A. Heinlein, Time Enough for Love
Zenna Henderson, Ingathering: The Complete People Stories of Zenna Henderson
Frank Herbert, Dune
Frank Herbert, Dune (series)
Homer, The Odyssey
Nalo Hopkinson, Midnight Robber
Robert E. Howard, the Conan (series)
L. Ron Hubbard, Battlefield Earth
Barry Hughart, The Chronicles of Master Li and Number Ten Ox
Aldous Huxley, Brave New World
Diana Wynne Jones, The Merlin Conspiracy
Robert Jordan, The Wheel of Time (series)
Guy Gavriel Kay, Lions of Al-Rassan
Guy Gavriel Kay, Tigana
Daniel Keyes, Flowers for Algernon
Stephen King, The Dark Tower (series)
Stephen King, The Eyes of the Dragon
Stephen King, The Stand
Katherine Kurtz, Deryni Chronicles
Tanith Lee, The Silver Metal Lover
Ursula K. Le Guin, The Dispossessed
Ursula K. Le Guin, The Left Hand of Darkness
Ursula K. Le Guin, A Wizard of Earthsea
Fritz Leiber, the Fafhrd & Gray Mouser (series)
Madeleine L'Engle, A Wrinkle in Time
C. S. Lewis, The Lion, The Witch and The Wardrobe
Stanislaw Lem, Solaris
Sergei Lukyanenko, Nochnoi Dozor (The Night Watch)
George R. R. Martin, A Game of Thrones
George R. R. Martin, A Song of Ice and Fire (series)
Richard Matheson, I Am Legend
Cormac McCarthy, Blood Meridian
Cormac McCarthy, The Road
Dennis McKiernon, the Mithgar (series)
China Miéville, Bas-Lag series
China Miéville, Perdido Street Station
Walter M. Miller, A Canticle For Leibowitz
David Mitchell, Cloud Atlas
L.E. Modesitt, Jr., the Saga of Recluce (series)
Elizabeth Moon, The Deed of Paksenarrion
Michael Moorcock, the Elric series
Michael Moorcock, The Eternal Champion (series)
Alan Moore, Watchmen
C. L. Moore, Shambleau and Others
Larry Niven & Jerry Pournelle, Lucifer's Hammer
Larry Niven & Jerry Pournelle, The Mote in God's Eye
Ben Okri, The Famished Road
George Orwell, 1984
Mervyn Peake, Gormenghast
Mervyn Peake, Titus Groan
Tim Powers, The Anubis Gates
Terry Pratchett, The Colour of Magic
Terry Pratchett, Hogfather
Terry Pratchett, Reaper Man
Philip Pullman, His Dark Materials
Patrick Rothfuss, The Kingkiller Chronicle
J. K. Rowling, Harry Potter (series)
J. K. Rowling, Harry Potter and the Philosopher's Stone
Joanna Russ, The Female Man
Brandon Sanderson, Mistborn: The Final Empire
Robert J. Sawyer, Calculating God
John Scalzi, Old Man's War
Mary Shelley, Frankenstein; or, the Modern Prometheus
Mary Shelley, The Last Man
Dan Simmons, Hyperion
William Sleator, House of Stairs
E. E. "Doc" Smith, the Lensman (series)
Neal Stephenson, Anathem
Neal Stephenson, The Baroque Cycle
Neal Stephenson, Snow Crash
Bruce Sterling and William Gibson, The Difference Engine
Mary Stewart, The Crystal Cave
Bram Stoker, Dracula
Theodore Sturgeon, E Pluribus Unicorn
Theodore Sturgeon, Some of Your Blood
Theodore Sturgeon, Venus Plus X
Jonathan Swift, Gulliver's Travels
James Tiptree, Jr., Her Smoke Rose Up Forever
J. R. R. Tolkien, The Hobbit
J. R. R. Tolkien, The Lord of the Rings
J. R. R. Tolkien, The Silmarillion
Jules Verne, 20,000 Leagues Under the Sea
Joan D. Vinge, The Snow Queen
Kurt Vonnegut, Slaughterhouse-Five
David Weber, Honor Harrington (series)
Manly Wade Wellman, Who Fears the Devil
H.G. Wells, The Time Machine
H.G. Wells, The War of the Worlds
T.H. White, The Once and Future King
Connie Willis, All Clear
Connie Willis, Blackout
Connie Willis, Doomsday Book
Scott Westerfeld, The Succession
Gene Wolfe, The Book of the New Sun
Virginia Woolf, Orlando
Roger Zelazny, The Chronicles of Amber (series)