If you're more looking for a perfected Ledger Joker impression, i'd recommend you watch CiscOreo's vids. He'll blow you away with it.
This is my favourite - http://www.youtube.com/watch?v=1wpX5BoWFuA
Scott McClure does great work but it's also still his unique way of it, I love his Joker for what it is. The whole Joker Blogs series really pulled me in and held my attention, highly entertaining to watch and the story unfolded awesomely.