Please be advised of the following information from the US State Department:

U.S. Citizens with Pending Passport Applications Allowed Temporary Travel Flexibility WITHIN WESTERN HEMISPHERE

WASHINGTON - The U.S. Departments of State and Homeland Security announced June 7, 2007 that U.S. citizens traveling to Canada, Mexico, the Caribbean, and Bermuda who have applied for but not yet received passports can nevertheless temporarily enter and depart from the United States by air with a government issued photo identification and Department of State official proof of application for a passport through September 30, 2007.  The federal government is making this accommodation for air travel due to longer than expected processing times for passport applications in the face of record-breaking demand. 

Adults who have applied for but not yet received a passport should present government-issued photo identification and an official proof of application from the U.S. Department of State.  Children under the age of 16 traveling with their parents or legal guardian will be permitted to travel with the child's proof of application.  Travelers who have not applied for a passport should not expect to be accommodated.  U.S. citizens with pending passport applications can obtain proof of application at http://travel.state.gov.

This accommodation does not affect entry requirements to other countries.  Americans traveling to a country that requires passports must still present those documents.  

For more information, visit the State Department's website - http://www.travel.state.gov/travel/cbpmc/cbpmc_2223.html 

Answers to Frequently Asked Questions can be found here - http://www.travel.state.gov/travel/cbpmc/cbpmc_3254.html