The Burnt World of Athas

The official Dark Sun website

Dark Sun, Dungeon World style and G+

Besides D&D & Pathfinder, Dungeon World seems to have gained some traction as a rules set for Dark Sun. You can find Travis Stout's excellent writeup of Dark Sun Classes for Dungeon World, there's also some equipment and useful tags such as Fragile for weapons.

Geneome talks about using Dark Sun with Dungeon World in : Dungeon World Defiling

Ritorix talks about his Green Age of Athas setting design for his PBP Dark Sun Dungeon World game.

On a non Dungeon World, but still Dark Sun note, G+ User Svebor Midzic found a cool article about ancient shark tooth swords that have a definite Dark Sun feel in the Dark Sun G+ Community.