In the Haskell tutorial's monads section they mention a paper by Wadler called "Monads for functional programming", and I finally looked it up the other day.
This paper uses some simple examples as motivation and builds in a straightforward way. I can see why they recommend it.
I understand the idea and goals of monads, but not the deep understanding I would need to explain the idea to someone unfamiliar with it. It requires more thought.
Writing that made me also want to look up effects systems: they've come up a few times in class and I understand why Cyclone uses one for modelling memory accesses, but I can't quite explain it. (The Cyclone stuff is black magic, though: they're not really mentioned in the manual because they've manage to make the compiler infer most of the effects of functions; so when you're reading about the language you don't even think about it. They go into it here.)
PS. There's a bit where their CVS bit their TeX: they wanted to talk about a type called "Id", so for TeX-speak they wrapped it like $Id$, and then CVS happily expanded that to include the filename and revision time. Nobody appears to have noticed, because it's in the postscript file I've been reading...
