The new edition of Dungeons & Dragons has fairly complete rules for using monster races as player characters. As such, many of the creatures in the "Monsters of Wildspace" section can be used in addition to those listed below.

Core Races in Spelljammer
Optional Races in Spelljammer
Additional races from WotC source.
New Spacefaring PC Races(2e)

Classes and Kits

Specialty Priests of Celestian(2e)
Specialty Priests of Ptah(2e)

Skills and Feats

Spelljammer Proficiencies in 3e*
A mapping of proficiencies from AD&D 2e to skills and feats in D&D 3e.
Spelljammer Skills and Feats
New skills and feats for Spelljammer.
More Skills And Feats
More skills and feats for Spelljammer

Spells and Psionics

Spells and Psionics for AD&D 2e(2e)
New Spelljammer-related spells and psionic powers.
Conversion of Spelljammer Spells to 3e
Epic Spells (sj3e)

Equipment and Magic Items

Spelljammer Weapons and Armor
Weapons from Spelljammer converted to 3e, along with some new additions.
Spelljammer Magic From the Encyclopedia Magica
Spelljammer-appropriate items from the Encyclopedia Magica books.
Works of Art
Treasures to find in your Spelljammer campagin.