Andy gives the talk "A pragmatic look at monads in Haskell" in the No Grownups Seminar. (Within an hour or two of publishing this, it was pointed out to me that this talk is really about the IO monad rather than monads in general, and that in particular the assertion that a monad represents a computation which performs a side-effect is not, in general true. A nice example is the Maybe monad. So a better title for this talk is "A pragmatic look at monadic I/O in Haskell".)