On Wed, 05 Aug 2015 02:02:13 -0700, grarpamp
Not quite the first that looks like a typical 'exchange', but the most substantial by far. This one's been known widely for 2mo and spoken for a year. And markets and boards exist in the past and present. It's necessarily closed system, and unnecessarily centralized. Have fun.
Only decentralized exchanges I have found so far are https://bitsquare.io/ and http://mercuryex.com/. To the best of my knowledge neither utilize an onion or garlic routing network to connect nodes. Agree that 'necessarily closed system, and unnecessarily centralized' are undesirable traits of ExchangeD.i2p. Ideal would be decentralized exchange platforms such as the Bitsquare are Mercury running using I2P as network transport.