EconGirl (Jodi Beggs) has some great new videos on Economists Do It With Models. They deal with taxes and, in my humble opinion, they are very good. There are two explaining the tax wedge and two explaining general rules about taxes.
I really enjoyed the first two. They provide clear explanation without shifting the supply and demand curves around. I found that makes it much easier for students to understand. I strongly recommend these to you if you need to brush up, or even to give to your AP students if they were absent the day of your stimulating presentation.
EconGirl has a whole series of videos. Check them out.