The extended cut will probably show the scene where Batman uses his bat-credit card to pay for all the property damage he's done. And in the nightclub scene where Batman nabs Maroni, he does the batdance first to try to blend in as just another club-goer.
The extended cut will also add back all of the Bam! Whiff! Pop! that was taken out of the cinema release at the behest of Warner Bros. If Nolan had his way, it would've stayed in.