अवतार on Nick 

Official nickelodeon site (american). It is a bit slow on the episode front, although book 3 episode released are all somewhere on the interent, this site is only up to what they have aired on television.
कीवर्ड्स: अवतार, avatar:the last airbender, official site, अवतार द लास्ट ऐर्बेन्डर, अवतार the last airbender