InstantDEX
- Website: http://www.instantdex.org/
- BCT Thread: https://bitcointalk.org/index.php?topic=684090.0
- Forum: http://forum.instantdex.org/
- Communicates with other nodes on a peer-to-peer basis, agreeing trades in a fully decentralised manner.  
- Can access many different sources of liquidity, including: blockchain-based asset exchanges (such as the NXT AE, etc), centralized exchanges via API keys (such as Poloniex, Bittrex, etc), and the Nxt Multi-Gateway.
- Each peer can provide their own API key information to connect to centralized exchanges to leverage any certain centralized exchange's liquidity
- Connecting to centralized exchanges' APIs is optional. Some may want a fully peer to peer trading experience, and can thus choose not to utilize a centralized exchange's liquidity. Meanwhile, those that do want a fully peer to peer trading experience can choose not to add centralized exchanges' API keys.
Weaknesses:
- The purely peer to peer trades currently only exist in Nxt Asset/MultiGateway form. Therefore, you are still trading IOUs which are susceptible to hacks/theft/insolvency.
- Integrates centralized exchanges. IMO, this goes against the whole point of DEXs.
- You need to run NXT, BTCD, and a InstantDEX node at the same time for full functionality.