I'd like to see a book of sandbox settings, similar to Points Of Light, but:
A) Ranging all over the place genre-wise, such as Mesopotamian, Sword & Planet, weird western in the vein of Stephen King's the Dark Tower, Transylvanian style gothick horrere, Lovecraftian colonial, fantasy Africa, Polynesian, native American, Viking Scandinavia, post-apocalypse, pre-Colombian mesoamerican, ancient India, southeast Asia, Atlantean, Rientsian gonzo fantasy, space station, age of cavemen and dinosaurs, etcetera, et al.
B) Being more "complete" with support material for the respective settings such as: one page dungeons, encounter tables, bestiaries, spells, equipment lists, and so forth.
Not only would this be a great resource for new campaigns but it would be great for extra planar travel, areas off of the known world of your campaign, other planets, cherry picking content for a campaign, and so forth.
Imagine such a product with the contributors being an all-star cast of OSTites!