Tendermint is a secure cryptocurrency consensus protocol that requires no proof-of-work mining.
It is an adaptation of an existing Byzantine consensus algorithm from academic literature (specifically the DLS protocol http://groups.csail.mit.edu/tds/papers/Lynch/jacm88.pdf). It solves the "nothing at stake" short range forking problem by requiring validators to post a bond deposit.
There is no official testnet yet, but I'll set one up soon. In the meantime please follow this thread or subscribe to the newsletter on the website for new announcements.
This is not a presale or launch of a currency. This is a call for developer and general interest.