Birthright 14
Blackmoor 22
Council of Wyrms 16
Dark Sun 25
Dragonlance 13
Eberron 21
Ghostwalk 14
Greyhawk 29
Jakandor 21
Kingdoms of Kalamar 19
Lankhmar 24
Mahasarpa 17
Mystara 27
Pelinore 16
Planescape 17
Ravenloft 12
Spelljammer 22
Thunder Rift 8
Wilderlands of High Fantasy 18
A lot of the settings have very little support. Ghostwalk is one of them and, unlike the others, I don't much care for it now that I'm actually aware of what it was trying to do.