My firm works with the Massachusetts League of Environmental Voters (MLEV), whose mission is to advocate for sound environmental policies and to elect pro-environmental candidates who will adopt and implement such policies. They are the state affiliate of the League of Conservation Voters.
MLEV publishes an annual Environmental Scorecard, which serves as a guide to how Massachusetts legislators voted on key environmental issues during the past legislative session (2007-2008). On page 2 of the attached PDF, MLEV quantifies the environmental savings from having produced their piece using responsible materials, based on calculations from the Environmental Defense Paper Calculator.
In addition, MLEV included several clean and recgonizable eco-logos on the back of the scorecard, underneath their return address on the mail panel.
These two transparent approaches (specific savings calculated and described inside as well as easy-to-understand labels on the outside) serve as a best practice for anyone in the marketing communications space.