Larry Lessig, Aaron Swartz, and others have put together p2p-Politics as a way of enabling people to point each other to political ads online.
From the site’s FAQ:
Does this have anything to do with p2p filesharing?
It is peer-to-peer, or people-to-people, but the files are not themselves shared. Only links to files are shared.
Where is the content hosted?
The Internet Archive hosts the content under a Creative Commons license. The links on our site and in our emails point to the Internet Archive.
Is Creative Commons sponsoring the site?
No. The site uses Creative Commons licenses to make it easy to collect and share the content, consistent with copyright. But Creative Commons is not sponsoring or supporting the site.