Part of the EELS team at the EF, I spend most of my day looking at the EVM from various angles, its potential edge cases and new features.

Guruprasad Kamath

An introduction and walk-through of the executable specifications for the Ethereum Execution Layer. 
Github (https://github.com/ethereum/execution-specs)

EELS is an implementation of the EVM in Python that has been optimised for readability. A great tool for EIP authors looking to prototype new ideas on the EVM, it is easy to understand as well as update with new features.