This thread's been a great help in advancing my trading, but still hard to find some, so build a comprehensive list.
Full list of trades:
Red gem < anvil < horseshoe < jewel < letter < wedding ring < hammer < fire arrows.
blue gem < old boot < heavy hammer < little bell < axe < rope < bridge plans < ice arrows.
yellow gem < bottle of wine < gold dust < magic mirror < spoon < skull < IOU < saw < light arrows.
green gem < map < broom < marmalade < croissant < beer < nail < empty bottle.
Trade locations:
item: timeline - location - received.
red gem: future - rocky mountains, top-left corner of map, fire rod needed in present - anvil. When anvil is in inventory, you can't run, and can't swim.
blue gem: present - warp to 9, house you need to list rocks to enter - old boot.
green gem: present - house where decedent of 2nd wise man was found (in future) - map.
yellow gem: past - main town, bartender - bottle of wine.
anvil - past - blacksmith (future, warp to 8, cross bridge to water temple, go to past) - horseshoe.
bottle of wine - present - rocky mountains, top-left corner of map, same place as red gem - gold dust.
old boot: present - upper-right corner of map, by large waterfall, approach whirlpool, and talk to monster to give him his "mother's vase" - heavy hammer.
map: present - main town, just outside 2nd from bottom-left house, sweeping woman - broom.
horseshoe: present - main town, lower-left house, unlucky man, go to future, talk to decedent - jewel.
gold dust - past - blacksmith - magic mirror.
heavy hammer: past - blacksmith - little bell.
broom: past - same place you got it from - jar of marmalade.
jewel: past - warp point 4, lower left house - letter.
magic mirror: present - hyrule castle, give to princess zelda - spoon.
little bell: past - present rocky mountains, next to temple, top of hill on right (need hammer), give to Santa (yes, THAT Santa) - axe.
jar of marmalade: future - same house as broom - croissant.
spoon: past - prison (N of warp point 9), give to prisoner - skull.
croissant: past - main town, bar, one of the knights - beer.
letter: past - prison (just N of lower right town on map), prison guard - wedding ring.
Axe : past: warp to 9, house where fish shop is in present, give to executioner - rope.
skull: past - warp to 9, go N, lift rocks to enter woods from south, give to guy at end of path (opera house location) - IOU.
beer: future - castle, give to ganandorf - nail.
wedding ring: past - warp point 9, lower-left house, give to prison guard's wife, go in basement - hammer.
rope: future - house next to temple of time - bride plan.
IOU - present - opera house, talk to guy with IOU, read all notes in all rooms of opera house and basement, talk to guy with IOU - saw.
nail: present - house next to temple of time - empty bottle.
hammer: present - house next to temple of time - fire arrows.
bridge plan: present - same house you got it from - ice arrows.
saw: present - house next to temple of time - light arrows.
Beginning of list made mostly from memory, so please correct me if I'm wrong about who gives what when. Will update as I get more trading done.
Interesting thing to think about

, the lady said the broom had been in family for generations, you got it from her, and gave it to her ancestor...the broom has no beginning, and has no end, the broom is a perfect circle, the broom cannot break or be damaged by the ravages of time, the broom is a perfect unchanging existence, the broom is god....
