You can check out 12 clips from the movie at Youtube. Use "dark knight iesb" for your search.

http://www.youtube.com/results?q=dark+knight+iesb&search_type=

Here's a new Joker clip that came out of nowhere and is 55-seconds long:

http://www.youtube.com/watch?v=Dgqew6mUtHY

My User Contributions master list - my initial post links are down but scroll down page to find list to active links