There isn't an animated continuation of Aang's story. The only other animated series in the Avatar universe is Korra, the avatar that follows Aang.

Korra takes the story through some very controversial changes, and production was frought with difficulties thanks to Nickelodeon constantly changing their minds on what they wanted. Season two is widely seen as the worst in the series by some distance, but season 3 redeemed it somewhat.

It's worth a watch for sure, just don't expect it to live up to the magic of the original.