This is great intro.
Dune - Composable build system for OCaml.
Esy - Package.json workflow for native development with Reason/OCaml.
mlsub - Prototype type inference engine.
Jane Street OCaml Workshop - Exercises and projects for Jane Street's OCaml Workshop.
OCamlFormat - Auto-formatter for OCaml code.
utop - Universal toplevel for OCaml.
Dune starter kit - Provides templates to help you start an OCaml project. It can be used to create multiple libraries, multiple executables, and test suites.