Take a Cartesian (or monoidal) closed category; define Reader monad for a given object E$E$ as X |-> X^E;$X \mapsto X^E$; and take a strong monad M $M$ (strong means preserves product or tensor product).
Now the composition M o E$M\circ E$ (M$M$ followed by E$E$) is a monad again.
At least I believe it is true; and I wonder if it is a known fact, or plain wrong.