Casper - arealive/Viper GitHub Wiki
Casper is a security-deposit based economic consensus protocol that is set to eventually replace the proof-of-work incentive system currently in place for the Ethereum public network. The developers working on CASPER include Vitalik Buterin, Greg Meredith, and Vlad Zamfir.
The ultimate proof of stake implementation will be deployed in Ethereum v1.1 AKA Serenity.