These are my ALL time favorite videos you have to watch! Type these into the internet adress. Though I must warn you, they don't load all the way sometimes.
There are also some videos I think are really nice in terms of characters pasts and the pain they've gone through. Like how Aang lost his grand father figure, how Zuko was betrayed by his family, and Naruto's pain from his childhood.
And then here are some awesome trailors set to avatar videos. My personal favorite is the Avatar set to Spiderman 2
And over here are some awesome pairings! You know, Toph Zuko, beacuse of their parents. And I have yet to get more!