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THE WORLD OF GREYHAWK![/size]
(Hah! You forgot I was a Greyhawk fan as well, didn't you!

)
I thought about a Non-WoTC setting but I heard most of those other setting are pretty bad.
You heard correctly.
Most are terrible. There are some that are better than what Wizards make, though. Much better. Much, much better. (Just ask Nightfall).
However, campaign settings are very personal things. What appeals to me (Greyhawk and Eberron) doesn't necessarily appeal to you. A lot of it is also tied up in nostalgia and other things.
So, here's a brief rundown of the two major D&D settings:
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Forgotten Realms[/size]
A large world, made up of mostly city-states and a few kingdoms or empires. As the main D&D world for the past... err... almost 20 years, it has a wealth of information published for it. The setting reminds me of a mediaeval society just going into the Renaissance. There are the remnants of ruined empires, and to some extent humanity is on the rise and other humanoids are on the decline.
The Forgotten Realms are a place of high magic: powerful wizards and warriors walk Faerun, and the threats can be equally dangerous. Despite the high magic of the setting, magic isn't that commonly used. It is used by the great, not so much the common people.
The foes range from regular D&D enemies (orcs lurking in buried dungeons) to societies of evil, the most iconic being that of the Zhentarim. Manipulation from behind the scenes is common in some adventures.
For some reason, there are great wilderness areas in the Realms, meaning that actual wars aren't so common. Intrigue between nations is more common.
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Eberron[/size]
Although Eberron is an entire world, most of the published material focuses on the continent of Khorvaire. Eberron is just coming out of a hundred-year war, which splintered a continent-spanning kingdom into many smaller domains. The result mistrust leads to a situation similar to that after World War II: the new kingdoms are trying to rebuild, they constantly scheme against each other, and the next war is just around the corner.
In stark contrast to the Forgotten Realms, there are very few powerful wizards or other magic-users in Eberron. However, low-level magic is very common, and is integrated into society.
So, magical devices such as the lightning rail (the train), elemental-powered airships and floating citadels do exist.
Foes tend to be secret societies, nations, or regular guys lurking in dungeons.
Adventures remind me of those of James Bond, Indiana Jones, and more darker sources.
As Eberron has only been around for about a year, there are fewer products to get and
much less information to absorb.
OTOH, it's much less "traditional" a world (or Tolkienesque, if you prefer), and so may be off-putting.
Cheers!