What about Mystara and Dark Sun? I know that DS is very unique in it's post-apoc style, but I was wondering about Mystara, the base for one of the best beat em' ups in history.
Mystara is... for lack of a better word, "gonzo." It grew from a simple map with a sentence or two describing each nation in module
X1 The Isle of Dread and the
Expert Set to a world spanning multiple product lines.
The original map showed one corner of a continent, with nations that were mostly very transparent analogues of Earth civilizations: a Roman/Byzantine Empire (Thyatis), the Arabian lands, three Nordic kingdoms a few miles north of that Arabian desert, a plateau where Mongols roamed (due west of the Nordic lands), a medieval Italy, a Native American land (right next door to medieval Italy and the shire of Hobbits, er Halflings), etc. Plus Elfland, Dwarfland, and Halflingland, a nation of wizards, a wasteland where monsters lived, and a couple of island kingdoms that seemed to be merchant/pirate realms.
The Gazetteer series launched in 1987 and started detailing each of the nations on the original Expert Set map in detail (first, 64 pages, later up to 96 and 128 pages), beginning with The Grand Duchy of Karameikos. It relied heavily on background material first appearing in the excellent adventure
B10 Night's Dark Terror, describing a newly-independent nation where the Duke was trying to secure his nation, keep the peace between the Thyatian settlers and the original Traladaran (medieval Eastern European) inhabitants, and keep his clearly-evil-but-he's-family cousin in check. This was a pretty fantastic product, and provided a level of detail never before seen in any TSR campaign settings (oh, but just you wait). It covered the physical and cultural traits of both human ethnicities, the religions of both human populations, economy and coinage, the military, the history of the land, notable personalities, factions, and adventure ideas. It also introduced a rudimentary skill system to the Basic/Expert D&D game.
The tone of the Gazetteers vary from one product to the next. Some are relatively serious, while others wander off into ridiculousness. Some are mostly serious but with increasing amounts of silliness creeping in. The Glantri book has a group of freedom fighters called the Elven Liberation Front, and one of the mage-princes likes to disguise himself as a wanderer named
Manuel of the Plains. The Alfheim book details several elven clans, including one where the three leaders look almost exactly like Cutter, Leetah, and Skywise from Elfquest. The Ierendi book describes the entire island kingdom as essentially a tourist destination and theme park for rich adventurers.
It took several years, but the Gazetteer series eventually covered all of the lands on the original Expert Set map, as well as a boxed set for the Empires of Thyatis and Alphatia. During this run, it was revealed that the planet was actually hollow, containing another world with its own sun, and the Hollow World product line was launched. There was an ongoing series in Dragon Magazine in which an airship was exploring the other continents and correcting the world map provided in
Set 4: Master Rules. These were later compiled and expanded, released in the
Voyages of the Princess Ark boxed set.
There is some truly great stuff in the Mystara setting, and I can't help but love it, probably because I started with the Basic, Expert, and Companion sets and the adventures that accompanied them. The material varies widely in quality, as it was only later on that there was any guiding vision for the setting. The original map is somewhat incoherent to begin with, given the small size of the area and the climactic zones which appear on it, never mind the Arabs living next door to the Vikings who live next door to the Mongols sort of thing.
The stand out products are
GAZ 1: The Grand Duchy of Karameikos, GAZ 3: The Principalities of Glantri, GAZ 6: The Dwarves of Rockhome, GAZ 8: The Five Shires, GAZ 13: The Shadow Elves, Dawn of the Emperors: Thyatis and Alphatia, and the
Hollow World boxed set.
At one point, TSR re-launched Mystara as an introductory setting for AD&D 2nd Edition with a couple of lavishly-illustrated boxed sets (with CD Enhanced adventures!). It's not as good, plus by that point TSR had inflicted Mystara with the same kind of metaplot shit as the Realms, so the timeline had been advanced, borders had changed, Elfland had been nuked and taken over by the shadow elves, and magic stopped working for one day every year.
So that was way longer than I planned...
At any rate, if you don't take your D&D settings too seriously, you could have a lot of fun with Mystara. Or if you're willing to toss out some of the silly and incoherent elements and rework them. In many ways it's more of a collection of mini-settings than it is a coherent setting in and of itself. You could run an entire campaign in one area and ignore everything else, if you wish.