There are many sites that instruct searchers on how to contact various people and institutions within the United States government. Here are a couple that I've dug up:
More Web Search Quick Tips
- Contacting the White House: Mailing address, phone numbers, and email addresses are all here.
- Contact Elected Officials: A one-stop shopping center courtesy of FirstGov. You can find out your state senator or representative's contact information, state governor, state legislative bodies, and more.
