Hi there!
uo-trade.net was a very popular trade platform some years ago, mostly for the german speaking community.
At the moment, people try to revive it, and because the website also is hosted/supported from a german team (those people mostly/all play on Drachenfels) this is the only shard which has auctions running (even though the website supports the english language).
There is a discussion going on at the friendly
UOB (Ultima Online Bibliothek, also german-speaking community) if some trade links should be integrated in the forum player profiles (a shortcut to uo-trade.net, because the actual "Markt" (=market place) on UOB is not very clearly arranged).
For me, uo-trade.net was/is one of the best plattform for bigger ingame trades, and I hope reviving it will soon be a success