This is an attempt to collect together, in tutorial form, a few of the things I've said about monads going back as far as my field guide. It's probably not a good first tutorial, but it contains things I'd wish I'd known immediately after reading my first tutorial.
Unfortunately, I used a few more LaTeX features than I ought to have while drafting it making it hard to get back into HTML form cleanly. So here is a PDF: Monads are Trees with Grafting.
Probably the main inspiration was this post by Derek Elkins.