I think you're letting your bias against Peter Jackson get a bit out of hand- it is extremely unlikely that the entire Mirkwood sequence will get cut, and Laketown will have to be in so they can showcase its horrific destruction.
Likely to be cut:
-The trolls. The depiction of trolls as basically stupid hillbillies is a poor fit with the giant savage monsters of Lot R
-The time stuck in the elven king's palace. Well, I don't know about how likely Jackson is to cut it, but it is a big chunk of the story with very little action.
Likely to stay:
-Gollum. For continuity with Lot R
-The Goblins. Needed to explain how Bilbo ends up in Gollum's cave.
-Smaug and the destruction of Laketown. Too spectacular to cut from a 3 D action film.
-The Battle of Five Armies, for the same reason as above.
-The Mirkwood Spiders, for the same reason as above.
-The opening Shire scenes.
Could go either way:
-Everything inbetween Smaug's death and the Battle of Five Armies.
However, knowing Jackson, he'll probably keep a lot of stuff in by making the film three to four hours long.