Hyperledger - Hyperledger is a multi-project open source collaborative effort hosted by The Linux Foundation, created to advance cross-industry blockchain technologies.
Blockchain Demo - Visual demonstration of blockchain technology
BlockCypher - AWS for Block Chains
Alethio - Powerful blockchain data, analytics & visualization platform
Nxt Platform - Ardor is a cryptocurrency and blockchain technology platform with tools to build successful blockchain applications out of the box. Scalable and easy to use.
LitePaper - Duolingo for blockchain.