In short, blockchain is a immutable linked list of hashes. Which can be used to solve the double spending problem in cryptocurrencies using proof of work (or other methods) and a persistent chain of records (blocks mined).
PoW: The more hashing power the more trust worthy.
PoS: The more coins the more trust worthy.
PBFT: Hand selected trusted nodes.
Randomized asynchronous algorithm: You trust nobody! Every single node is constantly re-evaluated. (Skycoin)
Horizon State - Digital voting.
Blockstack - Decentralized apps on Blockstack let you own your data so you can maintain your privacy, security and freedom.
Cardano - Cryptographic currency implementing Ouroboros PoS protocol.
Iden3 - Decentralized identity management solution.
Gnosis - Through blockchain-based, decentralized platforms, we enable the redistribution of resources—from assets to incentives, and information to ideas.
Let's build a blockchain! — A mini-cryptocurrency in Ruby (Haseeb Qureshi) (2017) - Great intro to blockchain.
EOS - Open source smart contract platform.
The Graph - Discover subgraphs by the leading projects in the Web3 ecosystem. All this data is immediately available for querying using GraphQL.
IELE Semantics - Semantics of Virtual Machine for IELE prototype blockchain.
Squeezer Framework - Build serverless dApps.
Castle Island Ventures - Venture capital firm focused exclusively on public blockchains.
Ara - Blockchain powered global rewards system.
Hedera Hashgraph - Enterprise-grade public network for decentralized applications.
Toychain - Minimalistic blockchain consensus implemented and verified in Coq.
Scilla - Smart Contract Intermediate Level Language.
Full Node - Aspiring blockchain node.