Does anyone have a complete list of the cut content? The material meant to be in the game but didn't make it for release?

You mean like the arena in Winterhold? I also recall several NPC's that apparently have quests or other stuff (like Grelka's quest or Nazeem's house).

I've never seen a complete listing made, but I'd start with the wiki.

There are a couple of earlier threads on the forums that make mention of it I believe.

Here's a few:
http://www.uesp.net/wiki/Skyrim:Unfinished_Quests
http://www.uesp.net/wiki/Skyrim:Unused_NPCs

From the major things, Civil War questline was meant to be much longer, but they decided to cut it because it was getting out of proportion compared to other questlines. Parts of Mephala's quest Whispering Door were also cut - initially it involved Balgruuf's death.