The response was... well, let me just say "Thank you" to BlasTech; if not for you this thread would have been totally dead.
Those only mentioned who do not actually appear are marked with a (*). In most cases, the strip indicated is the one where their name is first mentioned.
My original list of characters:
Adrin(*) - levmage of Freeman downs; father of Alan
http://npc.keenspace.com/d/20020414.html
Deep Green - leader of the Gragum following Quentyn's rescue of Nessie
http://npc.keenspace.com/d/20040213.html
Farthing - student at the College of Artifactors and Alchemists
http://npc.keenspace.com/d/20040106.html
Feld - Arbiter of Freeman Downs
http://npc.keenspace.com/d/20020519.html
Inkling - professor at the College of Artifactors and Alchemists
http://npc.keenspace.com/d/20040105.html
Oakroot - Tree Ape, delivery beast
http://npc.keenspace.com/d/20020915.html
Oombaw(*) - friend of the swamp chieftan's family
http://npc.keenspace.com/d/20040320.html
Pinky - BigDigger (star-nosed mole); pet/farming beast for Quinn's family
http://npc.keenspace.com/d/20020127.html
Raintree - healer for the Millfolk family
http://npc.keenspace.com/d/20050327.html
Riddick - associate of the Millfolk
http://npc.keenspace.com/d/20041025.html
Rint - scout from the swamp village
http://npc.keenspace.com/d/20021229.html
Rose - one of the Elders of Freeman Downs
http://npc.keenspace.com/d/20020609.html
Characters mentioned in the ensuing discussion:
Fleet(*) - historical Questor
http://npc.keenspace.com/d/20041127.html
Aislynn - artist at the "Fact & Opinion"
http://npc.keenspace.com/d/20040828.html
Miller - resident of Freeman Downs, father of an apprentice tinsmith
http://npc.keenspace.com/d/20030525.html
Abram(*) - historical Questor
http://npc.keenspace.com/d/20050130.html
A couple of questions about these come to mind:
Is either Pinky or Oakroot one of the oft-mentioned "bigdiggers"?
Is Miller Rahan's father?
Plus there is the aforementioned question about "Conner"
http://npc.keenspace.com/d/20041127.html
A few other names you might not have recalled:
Quinn is Quentyn's father.
Arith is the swamp chieftan.
Cole and Marta are Lord and Lady Millfolk.
I could not find names for Quinn's wife/Quentyn's mother, Arith's wife/Nessie's mother, the Frog Mage, and the Elder/farmer's militia teacher in
http://npc.keenspace.com/d/20020616.html.
edit - updated per RHJ's reply