There's World of Dungeons, which you can get from John Harper's blog The Mighty Atom. It's short, it's free, go get it.
There's the Goblin World hack (with it's own forum below), but it's about goblins.
There are a couple re-skins of Conan for AW, both called World of Conan I think, if that kind of fantasy is your thing.
There are at least 4 hacks of AW for Game of Thrones/A Storm of Ice and Fire. There's a forum for one below, and Pheylorn has one he linked to from the Story Games forums. I have one but I'm still working on it, and I think Brendan Conway has one he hasn't released yet. If that kind of fantasy is your thing.
There's a Dark Sun hack or two out there as well, if that kind of fantasy is your thing.
The best one is obviously Dungeon World, because it is a) completely finished, and b) extensively playtested. Oh, and c) has the most fans. So probably you want to go with that one.