Check out this good article that was posted for American Libraries this week: "Will Social Media Activism Rescue Besieged Libraries?" by Cindi Trainor. It's a brief overview of how librarians and their supporters have been using Facebook and Twitter to inform (and incite) the public about possible budget cuts. It has links to many of the major budget stories from the past few months.
If you're not using social networking sites in your library system yet, here's one more reason to try it out... building a following before you have a crisis is always a good strategy.