Material in The Drawing Board is a good source for new ideas. It contains mostly unfinished or very unconventional material that didn't make it onto Beyond the Moons.

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Crystal Spheres

The Vodoni Empire

Places of Interest

Monsters

Non-player Characters

Ships and Crews

Campaigns

Archaeusspace
The Talislantia crystal sphere for Spelljammer
Dark Sun Sphere
Ideas for the world Athas in Spelljammer
The Guardians
An original campaign.
Ravenspace
Ideas for the using Ravenloft with Spelljammer

Crossovers

Pernspace
A sphere based on the Pern books.
Star Trek to Spelljammer
Star Wars to Spelljammer