Sure there are. Here you have some pics from a few thread on this issue we had some years ago (most of them by courtesy of Manchild, googler extraordinaire):
Role of helmets in aerodynamics
Helmet aerodynamics (prehistoric thread, I'd say)
Helmet's aerodynamics (even older)
Schuberths small wind tunnel to build helmets
ATOS system
Helmet with splitter (similar to the one used by Button and a few drivers back in the 90's)
Some times it's better to use the search feature of this forum (altough most of our threads appear in the first page of Google searches nowadays, sometimes they are interred in page 3000, specially the older ones).