while this wont help with the humidity, i do find it very useful.
Windscoop™ Ventilating Sail by Davis
there is an emerson quietcool installed in the vee berth, but it is kind of a big pain to install and mine is on her last legs im afraid.... so
for the really
hot days i fire this off:
Carry-On Portable Air Conditioners - Marine Boat
and it does a fine job