For example, we're already planning an upcoming storyline that will involve the universe from Garth Nix' Sabriel, Lirael, Abhorsen books.
Phillip Pullman's His Dark Materials trilogy is also on the list, and we've been talking vaguely about ways to incorporate the following:
Kids books: Animorphs, Harry Potter, Beatrix Potter, Dr. Doolittle, The Westing Game, Hardy Boys, Nancy Drew, Roald Dahl (the Witches, the BFG, Matilda), Mother Goose, Oz, Brothers Grimm, Hans Christian Andersen, Artemis Fowl, E. Nesbit, Edward Eager, The Sorcerer's Apprentice, Boxcar Children, Bedknobs and Broomsticks, the Borrowers, Peter Pan, Redwall, Alice in Wonderland, Dr. Seuss
Sci fi: Star Wars, Star Trek, Asimov (Robot shit), Heinlein, 2001 Space Odyssey (someone play HAL pleeeeeeeeeease! ~s.), Ray Bradbury, Tom Swift, Lost in Space, Galaxy Quest, Vonnegut, The Tripod Trilogy, Orwell, HG Wells
Piratey/sailing stuff: the High Seas trilogy; Treasure Island; 20,000 Leagues Under the Sea; the Odyssey; Kidnapped; the Cay; True Confessions of Charlotte Doyle; Two Years Before the Mast; Island of the Blue Dolphins (if someone wants to play the girl after the book); Horatio Hornblower; Master and Commander
Fantasy: Madeleine L'Engle, Discworld, Sandman, MOMO, Xanth, Susan Cooper, Robert Aspirin (The M.Y.T.H. books), Lloyd Alexander, The Princess Bride, Tolkien, The Enchanted Forest Chronicles, The Bible
Historical fiction: Robin Hood, Ivanhoe
Classical lit: various Shakespeare plays (12th Night), Poe, The Deerslayer, Dickens, the Scarlet Letter, Prometheus Bound, Virgil, Dante, Livy, Ovid, Chaucer, Cervantes, Marlowe, Faulkner, Mark Twain
Mythology: Greek Myths (Jason and the Argonauts), Dreamtime and Australian mythology, Ancient Egypt, Norse mythology, Native American stuff, Celtic stuff (obviously), African mythology, Gilgamesh, Arthurian stuff (Holy Grail)
Horror: Dracula and other vampires/werewolves/gothic fantasies
Comic books: Justice League, X-Men, League of Extraordinary Gentlemen, Sandman, Various Mangas (Inu-Yasha, Sailor Moon, Pokemon)
Genre stuff: Western & Noir Dime Novels, Really Bad POTC Fanfic, Catch-22, Wild, Wild West, Maverick, Jules Verne
Theater: Death of a Salesman, Broadway Musicals (Into the Woods, Wicked, Phantom of the Opera, Passion, One on this Island, HMS Pinafore, Pirates of Penzance, the Music Man), Les Miserables, Beckett, Evita
People to play: Walt Whitman, Emily Dickenson, ee cummings, various historical characters (a la Alexander the Great and Julius Caesar), Mozart, Napoleon, Forrest Gump, various U.S. presidents
If you have any ideas as to how to incorporate these things (especially if you haven't gotten to play with any famous stories in the game so far) or if you're looking for a way to get into the game for the first time and one of these catches your interest, get in touch with me or Sara and we'll work something out.