We've been working on proof-of-stake and blockchain scaling/interoperability infrastructure since 2014. It all starts with a classical BFT algorithm which provides simple light-client proofs and fork-accountability. Your mobile phone can verify transaction finality in 5 seconds, with no need for an hour of block confirmations as in Bitcoin proof-of-work mining.
https://github.com/tendermint/tendermint <-- blockchain consensus engine
https://github.com/cosmos/cosmos-sdk <-- blockchain framework in Go
https://github.com/keppel/lotion <-- blockchain framework in JS
https://github.com/cosmos/voyager <-- blockchain explorer
https://github.com/tendermint/go-amino <-- blockchain codec derived from Proto3
https://cosmos.network
https://tendermint.com
Disclaimer: I'm a cofounder of the Cosmos project, cofounder of Tendermint, and long-time HN lurker.