Effective Petition

We have effective giving platforms to guide people what to do with their money. We have effective career organizations to guide people what to do with their professional time. We have an effective thesis website to guide academic researchers and students. But what about effective ways that people can do in their spare time? In particular, signing petitions or sending action mails is very easy for the broad public. So, what about an Effective Petition online platform that helps people sending the most effective action mails or signing the most effective petitions? I'm sure some effective altruists must have thought about this, but I still can't find an online website where I can sign the most effective petitions or that redirects me to such petitions, or that offers me sample letters and targets for effective e-mail campaigns,...  Shouldn't we set up such an online platform and Effective Petition organization? Perhaps something for Ambitious Impact Charity Entrepreneurship? I'm willing to help/volunteer, but am not able to do the technical stuff like webdesign and all. I can help content-wise: looking for the most effective petitions based on the Importance, Neglectedness, Tractability framework. Is anyone willing to collaborate on this project?