http://www.congress.org is a great website to keep up with current legislation that is under active debate. To get started, you can register for free by clicking "Register" in the upper right-hand corner of the home page.
After you get your confirmation email, you can log into the site. Then you will have access to create messages directly to your state and federal representatives. There are also many opportunities to join in discussions on various issues and voice your opinions for others to see.
For example, you can get on your soapbox like I did: