Took this from Jawajames:
The most significant SF/F novels from 1953-2006 according to Time. Bold the ones you have read, strikethrough the ones you read and hated, italicize those you started but never finished and put a star next to the ones you love.
1. The Lord of the Rings, J.R.R. Tolkien *
2. The Foundation Trilogy, Isaac Asimov *
3. Dune, Frank Herbert *
4. Stranger in a Strange Land, Robert A. Heinlein
5. A Wizard of Earthsea, Ursula K. Le Guin
6. Neuromancer, William Gibson - Keep meaning to pick this one up.
7. Childhood's End, Arthur C. Clarke
8. Do Androids Dream of Electric Sheep?, Philip K. Dick
9. The Mists of Avalon, Marion Zimmer Bradley
10. Fahrenheit 451, Ray Bradbury *
11. The Book of the New Sun, Gene Wolfe
12. A Canticle for Leibowitz, Walter M. Miller, Jr. - I love this book, I just need to actually finish it.
13. The Caves of Steel, Isaac Asimov
14. Children of the Atom, Wilmar Shiras
15. Cities in Flight, James Blish
16. The Colour of Magic, Terry Pratchett
17. Dangerous Visions, edited by Harlan Ellison
18. Deathbird Stories, Harlan Ellison
19. The Demolished Man, Alfred Bester
20. Dhalgren, Samuel R. Delany - I've read a couple others by this guy. Good writer.
21. Dragonflight, Anne McCaffrey
22. Ender's Game, Orson Scott Card
23. The First Chronicles of Thomas Covenant the Unbeliever, Stephen R. Donaldson
24. The Forever War, Joe Haldeman - Also meaning to read this one.
25. Gateway, Frederik Pohl
26. Harry Potter and the Philosopher's Stone, J.K. Rowling - Fun read, but it shouldn't be on this list.
27. The Hitchhiker's Guide to the Galaxy, Douglas Adams * Should be higher on the list.
28. I Am Legend, Richard Matheson
29. Interview with the Vampire, Anne Rice - Reading this now for class.
30. The Left Hand of Darkness, Ursula K. Le Guin
31. Little, Big, John Crowley
32. Lord of Light, Roger Zelazny
33. The Man in the High Castle, Philip K. Dick - My friend Jim keeps telling me to read this.
34. Mission of Gravity, Hal Clement
35. More Than Human, Theodore Sturgeon
36. The Rediscovery of Man, Cordwainer Smith
37. On the Beach, Nevil Shute
38. Rendezvous with Rama, Arthur C. Clarke *
39. Ringworld, Larry Niven *** - I love this book. Why the hell is it at #39? It should be #3 at least.
40. Rogue Moon, Algis Budrys
41. The Silmarillion, J.R.R. Tolkien
42. Slaughterhouse-5, Kurt Vonnegut - Need to read.
43. Snow Crash, Neal Stephenson - Need to read.
44. Stand on Zanzibar, John Brunner
45. The Stars My Destination, Alfred Bester
46. Starship Troopers, Robert A. Heinlein
47. Stormbringer, Michael Moorcock
48. The Sword of Shannara, Terry Brooks
49. Timescape, Gregory Benford
50. To Your Scattered Bodies Go,Philip Jose Farmer
That's a pretty good list, but there's some that really should be on there. His Dark Materials Trilogy, Solaris, The Moon is a Harsh Mistress, 2001: A Space Odyssey, American Gods, all those have a place there.