SOR> I've heard that Monads are in some way like Monoids, hence the
SOR> name. But I don't understand the explanation yet myself :(

Just compare:

Monoid: a set M with maps ident: M^0 -> M and product: M^2 -> M

(here M^0 is a one-element set)

Monad: a functor M with natural transformations return: M^0 -> M and
join: M^2 -> M

(here M^0 is an identity functor)

I had forgotten that the identity element was from M^0 -> M. In my gut I always feel it should be something more like M -> M, though I realize (as Stefan pointed out) I'm thinking too much in set-terms and not in category-terms.

David