101 Dalmations was based on the book The Hundred and One Dalmations by Dodie Smith.
The Cinderella tale (the basic plotline anyway) has possibly been around since early antiquity. An ancient Greek historian named Strabo recorded a tale of a girl named Rhodopus who had 'rosy cheeks' and lived in Ancient Egypt. One day, her sandal got supposedly snatched by a bird when she was out bathing and the bird deposited the sandal into the kings lap. Admiring the make and model of the sandal and thinking it strange that a bird had dropped footwear onto his lap, the king sent out his people to try and find the girl who the sandal belonged to. She was found and brought back to the King and they were married. There are Cinderella-esque tales in many cultures, including: China, Indonesia, the Philippines, Vietnam, Malaysia, Korea, Britain, and West and South Asia in the form of a few tales from Arabian Nights. The tale superceded Perrault even by a few years by Giambattista Basile who wrote a story of "Cenerentola" in 1634, though the tale seemed to fall by the wayside when Perrault's version came out 63 years later. In the early 19th century, the Grimm Brothers penned the tale in their own Germanic kind of way that involved a lot of eye-pecking and gore. Yay. Cinderella is still being re-imagined today in movies and books. Tale as old as time, song as old as rhyme--oh wait, wrong story. Sorry.
Lady and the Tramp was half original, half not so original. Lady was based off of the English Springer Spaniel of the same name that belonged to a story man from Disney. Lady was moved aside because of a new baby in the house, and so he approached Disney with sketches in 1937. He got the go ahead and started storyboarding, but Disney thought the arc was too sweet and not action-centered enough. So in the early fourties, Disney read a short story by Ward Green called "Happy Dan, the Whistling Dog" and suggested that Lady fall in love with a dog like Happy Dan. Disney bought the rights to the story and bada-bing, you've got yourself Lady and the Tramp.
Wreck-It Ralph is an original story that includes plenty of cameos and nods to our favorite video games. Characters come from games like Mario, Pac-Man, Sonic the Hedgehog, Q*bert, Altered Beast, Street Fighter, Paperboy, Pong, Quix, Frogger, BurgerTime and Dig Dug. Nods are included to other games like a mention of Lara Croft, graffiti referencing: Final Fantasy VII, Zero Wing, Street Fighter, and World of Warcraft, and an exclaimation point from Metal Gear.
Dumbo was a very small childrens story that was only 8 drawings and a few lines of text written by Helen Aberson and illustrated by Harold Pearl that served as a demonstration of a storytelling toy called Roll-A-Book--published before 1939 which was the year it was brought to Disney's attention.
Bambi was originally a book named Bambi, A Life in the Woods by Felix Salten written in Austria in 1923 and is acclaimed as one of the first environmental novels ever published. Originally in German, it was translated and brought to North America in 1928.
Info taken from personal knowledge and wikepidia.