Bitcoin's Lightning Network Alpha Release
lightning.community
lightning.community
Lightning is a protocol built on top of bitcoin that allows the trustless transfer of Bitcoin without settling to the chain. These transfers don't need to be individually mined and don't take up capacity on the main chain.
The main drawback is that it requires locking up collateral in a "payment channel" between two peers.
IMHO lightning could be the backbone of some interesting micropayments/exchange architecture in the future.