Treacy Kirkpatrick, of Washington, D.C. argues that the the ballot box provides the avenue for environmental action. Vote for candidates with a pro-environmental position, and let them know about the issues that concern you. The League of Conservation Voters will help you track your own representative's voting record on environmentally related issues. They maintain a WWW server that provides a "scorecard" based on their determination of whether the representative voted pro-environment. A link is provided below.
To look at a "scorecard" of your congressman's votes go to the League of Conservation Voters web site.