This is a fascinating read about the original script for Avatar and how it differs from the final product:
http://chud.com/articles/articles/21969/1/PROJECT-880-THE-AVATAR-THAT-ALMOST-WAS/Page1.html
The differences are amazing, some of the things listed would have made a big difference in the movie and certainly made the story a little less derivative in bits. This is a long read, but worth it!
I wonder if we’ll see a special edition at some point with some of the missing scenes… ya gotta figure that the cost of rendering will continue to drop, maybe it’ll eventually be a matter of Cameron sitting down at his PC with coffee and slapping out another hour of footage on his Mac 2020 before heading out to swim in his money bin. 