alrighty, i'm currently buying the following items at any quality:
linen
steel
chantrelles
blueberries
cavebulbs
silver
brill, roach, sturgeon
silk
jorbonzola
any metal
and i have the following things available to sell:
q80ish metal (cast iron, copper, tin, bronze)
q100+ metal
q140ish cheese trays, curding tubs
farm hats, chef hats, spectacles, bear capes, bear talismans, of various (high) quality
high q fishing gear (quality varies on these but they are all really high)
crafting services - i currently have 142 base dex and 196 base sewing.
unfired treepot crafting with your clay, leather crafting with your leather, sewing with your cloth, etc. armor, swords, etc. as well, pretty much anything in the craft menu i can make high q.
i could perhaps come tame an animal for you as well if you live somewhere relatively accessible and have aurochs or mouflon spawns nearby that don't require crossing a river to get back to your settlement.
lots of other stuff, you want it, i have it or can make it or get it.
current rates for a bar of common metal 24 linen, 16 chantrelles, or 12 blueberries per bar