I'm going to repost my question from a recent F# item and I hope it'll get some traction this time:

I learn a lot by reading others' code. Can anyone recommend a a project or two that is small enough for a newcomer to wrap their minds around, that also exemplifies what makes a high quality F# codebase?

Giraffe for sure:

https://github.com/giraffe-fsharp/Giraffe

As an added bonus you'll learn a very popular tool for sticking a web interface in front of your F# app.