There are a number of petitions going around about this issue, but Consumers Union has a long history of fighting specifically for consumer rights, which is why I recommend signing theirs. Here are excerpt from there website:
“There is still time for you to be a part of this year’s most amazing David vs. Goliath story.
Nearly 900,000 Americans – individuals just like you who want freedom of choice, not one giant corporation telling you what you can and can’t have – have joined together to stop Comcast’s domination plan. And they are making a huge difference.
Will you join them, and help us get to one million-strong? Just sign our petition to the FCC to stop the Comcast-Time Warner merger, and you will be part of this historic battle!”
Click the following link to learn more and sign the petition: