Escrow contract (with 3rd party arbitration.)

https://github.com/Open-Transactions/Open-Transactions/blob/master/scripts/smartcontracts/escrow/escrow.otc


Two-way trade contract (similar, much simpler -- only 2 parties.)

https://github.com/Open-Transactions/Open-Transactions/blob/master/scripts/smartcontracts/two_way_trade/trade.otc