This is great intro.
Dune - Composable build system for OCaml.
Unix system programming in OCaml
Esy - Package.json workflow for native development with Reason/OCaml.
mlsub - Prototype type inference engine.
OCaml for Haskellers
WebAssembly backend for OCaml (2018)
Jane and the Compiler (2018)
Jane Street OCaml Workshop - Exercises and projects for Jane Street's OCaml Workshop.
HN: OCaml for the masses (2011)
Solutions to Functional Programming in OCaml MOOC course
The OCaml Platform 1.0 - Reason ML (2018)
OCamlFormat - Auto-formatter for OCaml code.