People have told me that Avatar: The Last Airbender is a fantastic little show that manages to overcome the typical kid's show boundaries using simple things like, oh, solid storytelling, personality and humor. I can't back this up, having never watched the show myself, but I'll take their word for it. Now, I'll have to ask them what they think about a "sequel series," set seventy years after the events of the finale.
It's called The Legend of Korra and will feature a "passionate, rebellious, and fearless teenaged girl" as a protagonist and when the show starts, "Korra will already have mastered earth, water and fire and seeks to control air. She meets Tenzin, Aang's son, and the two begin Korra's airbending training while dealing with the dangers of a growing anti-element bending revolution."