I think web petitions are the closest thing to useless that there is, but if you agree with them, it doesn’t take any time to sign them. So, go sign the Reclaim the Public Domain Petition. As Larry Lessig points out, the only way to get the government to adopt a saner legal model for intellectual property is to get people to care enough about them to make them election cycle issues. One way to do so is to get politicians to start talking about these issues, and another way is to build a grassroots movement that talks about these issues. The good news is that they’re not mutually exclusive, so let’s do both.
Speaking for myself, I’ve been concerned about copyright term extensions since the Bono Act in 1998 (because I read a mailing list post about them by John Levine at the time), but I didn’t really understand the full value of the public domain until recently. That said, I’ve always liked Dover Thrift Editions — ultracheap printings of works that are in the public domain.