http://sharedcoin.com/ is
trustless centralized CoinJoin by Greg Maxwell.
Darksend in DarkCoin is
dezentralized CoinCoin by Evan Duffield.
Is dezentralized trustless CoinJoin possible? Ring signatures on Bytecoin and Monero?
Even though ring signatures are far more secure, far more decentralised than MasterNodes, people here don't like them because of the "bloat."
The bloat is a chain that is perhaps 2 to 3 times larger than a conventional chain.
To me, 3 times space requirements for this technology is worth it.
Anyway, I'll be quoted and dismissed for saying that here. :p