A few months ago, I tried to arrange a community project called the Desolate Dustcrawl, in which sixteen different people directed the creation of one dungeon each, contributing additions to each other's dungeons. These different adventure locations would be put on a simple shared hexmap, with some basic lore tying them together as sites in a ruined city wracked by desertification and an angelic reckoning.
It didn't come together. People were keen to sign up, but did not have much extrinsic motivation to arrange their dungeons, or to contribute to each others'. I consider it a light failure; did not coalesce, but without much ventured on my part.
Now, we did get something from this, a couple dungeons complete enough to salvage. The first I will post here, the Sunken Tomb of Honors. Thanks to SunderedWorldDM, purplecthulhu, and especial Random Wizard for their contributions. The map is a creative-commons map available from Dyson Logos