They added the Huorns back to Helm's Deep!
And added scenes with Merry and Pippin in Fangorn! (Loved the Entdraught scene. And Treebeard reciting poetry and pining for the Entwives.) And had them find the pipeweed stash in Isengard after the flood!
*cheer*
And they added a flashback that explains why Faramir was so anxious to prove himself to his father, which was a nice touch. And added a scene with the Elvish rope, and a scene explaining that Sauron fears Isildur's heir, and extended the scene in Osgiliath after Faramir lets Frodo and Sam go, and and and and...
*giggle* Aragorn's age. That was fun. Hee.
And the final count of the orc-killing of Legolas and Gimli. "He's twitching because I have my axe embedded in his nervous system!" Bwahahaha. XD
So yeah. Loved the extended edition of The Two Towers.
Now the only thing making me grumpy is I have to wait another two months for the release of The Return of the King. (Look at the release dates.) *grumble*
But apart from that, I'm happy. Can't wait to dig in the extras, commentary tracks, etc.
[EDIT] This site has a pretty thorough list of the scenes that were added.