Jambe did a little research in this field. Combined with what we know and what The Starkiller has found I guess we have a list that looks something like this:

Star Wars:

Introductory Crawl is Spoken.

ESB:

Video:
The Emporer does not fade in in his communique with Vader.
Millenium Falcon Satellite dish not visible with Luke on weather vane.

Audio
- Han saying 'watch this' as he tries to jump to hyperspace in the asteriod field. Although the dialogue hasn't changed different emphasis are put on certain words."
- Luke - "I don't pick up any life readings" - Different take
- Han - "I'm going back" - Different take
- More rebels calls of 'retreat' when Walkers attack
- Leia "They're getting closer [star destroyers] - Different take - she stutters it twice
- Cloud Car pilots - Different line - will confirm with actual line asap.
- Leia "I know where Luke is" is replaced by "we must go back" or something similar
- C3P0 - new line just before "I thought that hairy beast would be the end of me" - It's something like "I'm glad we are back together"
- The frigate at the end looks decidedly different - i will have to check this.
Cloud City Security - "Any aggressive move will not be tollerated!"
Cloud Cit Security - "Permission granted to land on platform 3-2-7. Any deviattion will" - Han cuts of comms.
Leia - "Lando, hurry up, we've got company!" (as Lando is rescuing Luke from the weathervane)
C3P0- "Get away from there, you don't know how to fix the hyperdrive!