Okay...deep breath:
Aladdin (MGM - Fantasmic!, MK - Tiki Birds, MK - Magic Carpets of Aladdin, MK - Mickey's Philharmagic)
Alice in Wonderland (MK - Mad Tea Party)
Beauty and the Beast (MGM - Beauty and the Beast, MK - Mickey's Philharmagic)
Bug's Life (Animal Kingdom - It's Tough To Be A Bug)
Dinosaur (Animal Kingdom - Dinosaur!)
Dumbo (MK - Dumbo)
Finding Nemo (Animal Kingdom - Finding Nemo: The Musical opening in late Nov/early Dec, Epcot - The Seas with Nemo)
Honey I Shrunk the Kids (Epcot - Honey, I Shrunk the Audience)
Lilo and Stitch (MK - Stitch's Great Escape)
Lion King (Animal Kingdom - Festival of the Lion King, Epcot - Circle of Life (Land), MK - Tiki Birds, MK - Mickey's Philharmagic)
Little Mermaid (MGM - Voyage of Little Mermaid, MK - Mickey's Philharmagic)
Mary Poppins (MGM - Great Movie Ride)
Peter Pan (MK - Peter Pan's Flight, MK - Mickey's Philharmagic)
Pirates of the Caribbean (MK - Pirates of the Caribbean)
Pocahontas (Animal Kingdom - Pocahontas and Her Forest Friends, MGM - Fantasmic!)
Sleeping Beauty (MGM - Fantasmic!)
Snow White (MK - Snow White's Scary Adventures)
Swiss Family Robinson (MK - Swiss Family Treehouse)
Tom Sawyer/Huckleberry Finn (not necessarily a Disney title - MK - Tom Sawyer Island)
Toy Story (MK - Buzz Lightyear)
Winnie the Pooh (MK - Winnie the Pooh)
Non Disney:
Alien (MGM - Great Movie Ride - RATED R)
Casablanca (MGM - Great Movie Ride)
Muppet Movie (any Muppet Movie but the first is the best) (MGM - Muppetvision 3D)
Raiders of the Lost Ark (MGM - Great Movie Ride, MGM - Indiana Jones Stunt Show)
Singing in the Rain (MGM - Great Movie Ride)
Star Wars: New Hope/Empire Strikes Back/Return of the Jedi (MGM - Star Tours)
Tarzan (with Johnny Weismuller) (MGM - Great Movie Ride)
Wizard of Oz (MGM - Great Movie Ride)
Of course, many of these attractions TELL the story of the movie in question (the Beauty and the Beast, Lion King and Little Mermaid shows for example) or are only tangentially connected (the tea cups ride does not require having seen Alice, for instance). It's not required to watch really any of these things.
I would say watch the ones that multiple attractions are based on: Nemo, Lion King, Aladdin, B&B, Mermaid.
While I wouldn't worry if I didn't recognize a character from a movie (you'll get more done in the parks that way

), but movies not on the above list that I've seen multiple characters from:
Jungle Book (Baloo and King Louie)
Pinocchio (Gepetto, Pinocchio, Jiminy Cricket (rare, but he is there), Gideon, Longfellow, Stromboli)
Robin Hood (Robin, Little John, Sheriff, Friar Tuck and Prince John)
all in all, enjoy your trip and maybe bring a little memo pad and if your child especially enjoys an attraction (or you realize that there is a character you know that they don't) you can jot down the movie and watch before your NEXT trip!