An interesting article on the McLaren snorkel system here: http://scarbsf1.wordpress.com/2010/03/11/235/
In brief, it allows air from the front of the car to be directed at the rear wing to increase straight line speed. The clever bit is that because movable aerodynamic parts are banned, it’s just a pipe with the drivers leg in the way. The driver just moves his leg to block airflow or enable airflow.
Elegant and cheap. All the other teams will moan but they’ll have it by the next race I’m sure.