Solidity Documentation (solidity.readthedocs.io)
Solidity Cheat Sheet And Best Practices (https://github.com/manojpramesh/solidity-cheatsheet)
Building a production-ready Ethereum DApp from idea to final product – Part 1 (https://blog.amr-gawish.com/building-a-production-ready-ethereum-dapp-from-idea-to-final-product-first-section-the-3b9975a226c)
CryptoZombies (interactive. +++++) (cryptozombies.io)
EthereumDev (https://ethereumdev.io/)
EthList: The Crowdsourced Ethereum Reading List (https://github.com/Scanate/EthList)
Coursetro (beginner) (https://coursetro.com/courses/20/Developing-Ethereum-Smart-Contracts-for-Beginners)
CRUD Part 1 (+++++) (https://medium.com/@robhitchens/solidity-crud-part-1-824ffa69509a)
CRUD Part 2 (+++++) (https://medium.com/@robhitchens/solidity-crud-part-2-ed8d8b4f74ec)
Learning Solidity (beginner → advanced. +++++) (https://www.youtube.com/channel/UCaWes1eWQ9TbzA695gl_PtA/videos)
One-To-Many CRUD (+++++) (https://medium.com/@robhitchens/enforcing-referential-integrity-in-ethereum-smart-contracts-a9ab1427ff42)
The Patient Smart Contract – Part 1 (beginner) (https://medium.com/@tejnikumbh/solidity-tutorial-1-the-skeleton-c311f1ea96b7)