First, here's a list of blogs doing the 30 Day D&D Challenge:
Know of any more blogs? Please send them to me so I can add them to the list.
That's easy: Domikka.
Domikka's my homebrew campaign setting I've worked on for over 20 years. It's about the decline of an Empire, the rise of an ancient race in the West, religious intolerance and fanaticism, the right to power. It mixes real-world history with fantasy. It's very anti-Tolkien (no elves, halfings, orc, etc.), but not quite as angsty as Moorcock.
That's five binders full of notes in the picture. This doesn't even count all of the documents I have on my computer.
Domikka's kind of an odd name. Why two "k"s. I couldn't tell you what my 13-14 year old brain was thinking--something do with language. Maybe I should take the extra k out, but its stuck.
The setting grew organically. Every time I'd run a new campaign, I used it as opportunity to develop another part of the main continent.
I've self-published a novella for Domikka, Murder on the Hot Flats, which is available for Amazon's Kindle.
A runner up would be The World of Greyhawk, both pre and post-Greyhawk Wars.