Short answer - a lot!
Magic Kingdom:
-New Fantasyland expansion opened (Seven Dwarfs Mine Train ride, Storybook Circus - Dumbo moved there and got a twin so now there are two side by side, Be Our Guest restaurant, Voyage of the Little Mermaid ride, Gaston's Tavern, Princess Fairytale Hall - meet and greet for Princesses)
-Mickey now meets at the front of the park and talks!
-New daytime Castle show - Mickey's Royal Friendship Faire (one of my favorites - it opened during my College Program so I have a soft spot for it)
-New nighttime fireworks show - Happily Ever After
-New afternoon parade - Festival of Fantasy (AMAZING!)
Epcot:
-Innoventions is basically no longer a thing. It has been replaced on one side by a Character Spot that contains Baymax and then also Joy and Sadness from Inside Out
-Soarin' is no longer traveling over California, but the movie has changed to be Soarin' Around the World (request terminal B to avoid a weird curve to all the sights)
Hollywood:
-Lots is closed in preparation for Star Wars Land and Toy Story Land (Backlots, Lights Motors Action)
-Great Movie Ride will be closed by the time you get there (tear)
-Frozen Sing Along Show - a MUST see for all ages, even if you are older and don't love Frozen. It's hilarious and a family favorite!
Animal Kingdom:
-It's open at night! Nighttime show (Rivers of Light), Tree Awakenings (gorgeous!), nighttime safaris
-Pandora Land of Avatar just opened with two new attractions, a quick service offering, and shopping. You've got to see it both during the day and at night - they are two totally different experiences!
Disney Springs:
-Formerly Downtown Disney, HUGE expansion with more shopping and dining.
-Disney Quest closed recently and La Nouba is leaving at the end of this year
