"A green action is something you do to reduce your environmental footprint".
I have found a couple of examples that points to the direction where i believe designers can contribute with key knowledge to facilitate green actions. The right information at the right time might enable you to choose the green action over the unsustainable action in the moment of the deciscion.
Prius consumption monitor
Toyota Prius is a good example for a system that display relevant information in the moment of action. The information encourages you to choose the greener action by visualizing the reward you would get by reducing your "pedal pressure". The reward in this case is more miles per gallon (MPG), which is a common parameter for comparing how economical a car is to drive. The screen also display how you are doing on a longer timescale by plotting data from the last 30 minutes. This seems to be enough encouragement, at least for this driver, to adapt a MPG optimized driving routine.
/update - Honda Insight which will compete against the Prius also sports an interface that encourages economical driving.
"The Personal Well-Tempered Environment"
Dan Hill, who operates City of Sound, has outlined a concept (blog|video) where information is the main driver for doing greener actions in our daily life. The idea is to collect all relevant information on consume and contribution of energy at home and sharing the data. This enables realtime resource mapping at an individual level, up to the neighbourhoood community and even city level. Information from this mapping, shown at the relevant point of descision, could change behaviour at many levels in a society.
API for buildings the concept connects to a larger social context that might impact citywide behaviour. In his video presentation Dan argues that the dashboard idea is a bit "geeky" and would rather have information in a tangible format outside of a screen. Dan raises a few concerns when inserting a lot of information into our daily life. Will it be stick or carrot? How can it be designed to inform without creating stress or moralize?
This is at the core concerning that given the right information at the right time people would choose the greener action.