If you're not familiar with this organization, be sure to check out their website for tons of great info and projects you can become involved with like: Reviving our oceans, building a clean green economy, saving America's wildlands, ...the list goes on and on. Click on the Take Action tab and maybe you'll feel inclined to sign a petition or send a letter to your Congressmen.
Bay area band Green Day has also partnered up with NRDC in an effort to get the word out through their fans. For more info: http://www.greendaynrdc.com/ Free wallpapers and icons are available to support the cause by clicking on their Free Stuff links. You can also sign up for their email updates and alerts, make a $10 donation and get a Dream and Differ dogtag, and more.