If you are unsure of where your representative stands, Save the Internet.com has a wonderful map that can help you find out.
I urge everyone to sign petitions. Call your Senators and Representatives. Write them letters. Send them email. Blog about it. Send a letter to the editor at your local paper. Do anything and everything to make your voice heard!
Update: This map doesn't show where everyone stands. I decided to contact Congressman Hobson (7th District, Ohio) to find out where he stands. My message was simple: "I wish to find out where you stand on the Markey amendment to the COPE Act and to urge you to please keep the Internet free and open by voting for enforceable network neutrality requirements in the future. Thank you."