If you've got 15 minutes
Reach out to your child's class parent and volunteer to send reminder e-mails for events, meetings, field trips, parties, or fund-raising. You can be a hero just for sending those e-mails from your phone while sitting in a carpool line!
Should candy vending machines be removed from the school cafeteria? Is the science lab hopelessly outdated? Do kids need bike racks or crossing guards so they can ride or walk to school? When something needs changing at home or at work, you speak up, right? So set up an appointment for a short meeting or phone call with the school's principal and let him know how you feel.
Establish a Twitter and/or Facebook page for your child's school or classroom (as an alternative to the school's official website and communication channels) where parents can have more of a voice. Get the discussion going on important issues like policy changes or anti-bullying initiatives facing the school or class, and brainstorm about ways parents can address them.
If there's something going on at your school that the community needs to know about, contact the local media. Send an e-mail or call a reporter at your newspaper, radio station, or TV channel if there's an issue you think could benefit from more public awareness and involvement. Or tell them about interesting classroom projects or student accomplishments—everyone loves a feel-good story.