Oathbound, the kitchen sink setting before Eberron. It is very high magic and power where the PCs are driven to either become more powerful or die- the reason for the name of the planet (the Forge). Decent support with a book coming out in the near future that updates it to 3.5. It also has a nice built in reason to allow everyother rpg book as a source.
There are 7 domains (3 have supplement support so far)- Penance is a megacity that is mostly ruins and filled with monsters (and the surrounding plains and smaller cities), Arena is a desert where armies clash daily over the gold and other metals under the sand, Wildwood is a forest and swamp where the lord encourages predators to kill the weak, Anvil is covered in mountains where wind wizards fight for dominance, Eclipse is mostly underground and the ruling races are thieves and undead, the Vault is a frigid wasteland where spellcasters create artifacts and are protected by undead, and the Kiln is a giant volcano with a pirate city at its base.
The Forge is a prison for a god and each domain has a ruler who wants to be free but is oathbound to only leave when defeated by a greater power. Thus they draw the best from the mulitverse in hopes of finding the one who will become powerful enough to take their place (they are called seeds when they arrive). They also draw monsters and items to test the seeds.
The other setting I suggest is Morningstar. It has artificers with living constructs, a living warning to the people, god like beings who are attempting to crush civilization, an ancient war between elves (nature spirits that gained flesh for a price) and dwarves (souls created by the mother godess to combat the elves), a kingdom of aberrations that is starting to make war upon the human lands and it set in the golden age of the world. It is also high magic to the point that powerful beings warp the land. The only downside is there is no support so far.
