1. The introduction of the new Minister of Magic and all that happens between him and Harry.
2. Dumbledore coming to the Dursley's house to give them a piece of his mind.
3. Harry, Ron and Hermione seeing Draco in the dress shop, and Harry getting his first idea that Draco had been branded into the Death Eaters.
4. The invisibility cloak was absent in almost every important scene besides the train.
5. Slughorn's parties (the first of which that was on the train when Ginny gets her first invite.)
6. Tonks finding Harry on the train.
7. Tonks and Lupin's relationship
8. Several key memories that help Harry find the horcruxes in the 7th book. Also the awkward arguments between Dumbledore and Harry about Dumbledore's whereabouts and what happened to his hand.
9. Hagrid and Thwarp
10. Harry finding out that everything that Sirius owned now belongs to him (including the house that serves as the hiding place in the 7th book)
11. Several of the Quidditch matches and how Harry ends up in trouble and has to miss the final match. THIS is when Harry and Ginny have their first kiss when she becomes the seeker for the team and helps the team win.
12. Harry and Ginny's relationship
13.Fleur and Bill's engagement, and are completely absent in the movie.
13. Madam Rosmerta's role
14. Moaning Myrtle's role
15. THE FIGHT IN THE CASTLE!!!! ARE YOU KIDDING ME! The best part of the book and they cut it out. They deserved to be fired in my opinion. How could Rowling sign off on them doing this!?
16. Dumbledore's funeral
17. Harry telling Ginny he could no longer see her...they couldn't have this scene considering they never showed them to be in a relationship.
I'm sure there is a lot more, but you get the idea. All of these scenes were cut to add those that never even happened in the book. If you are an actual fan of the book, be prepared to be disappointed. If you haven't read the book, I'm sure it'll be great.