expand_less (note that this list is not exhaustive)

Anything else by Radiance House
Anything else by Rite Publishing
Anything else by Fantastic Gallery
Anything by AAW Games
Anything by Frog God Games / Necromancer Games
Anything by Green Ronin Publishing
Anything by Hammerdog Games
Anything by Kobold Press
Anything by Legendary Games
Anything by Playground Adventures
Anything from the Mystara fansite: http://www.pandius.com/