2nd Edition-specific setting that was never to my knowledge updated to newer editions. Mad Max-style setting done 1000 times better than Mad Max. The best desert setting and desert-set adventures ever. So much imagination has gone into it that it includes more variety than Greyhawk or DragonLance, worlds which do not restrict themselves to an endless desert.
http://en.wikipedia.org/wiki/Dark_Sun
Dark Sun is a Dungeons & Dragons campaign setting featuring the fictional desert world of Athas. The original Dark Sun Boxed Set campaign setting was released in 1991.[1]
The themes of this setting could fit in the Dying Earth subgenre and include survival against the elements, ecological disaster, resource depletion, survival of the fittest, slavery and poverty, and the widespread use of psionic abilities. The political setting is similar to ancient Middle East, North Africa or Mesopotamia. Water and metals are extremely scarce. Survival against the elements has made it a harsh exotic world.
Characters need to look for water every day or face special dehydration rules. Magic use destroys the vegetation of the planet (which is why it became a desert in the first place).
Dark Sun wizards include defilers, whose powers come at the expense of the ecosystem, and preservers, who wield magic in concert with the environment. Illusionists specialize in illusory effects and may be either defilers or preservers.
Psionic classes
Psionic power is very common on Athas. Every player character has psionic abilities, as do many NPCs.[5] Psionic ability is about as common in Dark Sun as arcane magic is in other D&D campaign settings, and it is accepted as a normal part of life. Schools of the mind exist, mostly maintained by and serving the Sorcerer-Kings.