Under the Western Hemisphere Travel Initiative (WHTI), beginning January 23, a passport will be required for anyone traveling by air between the United States and Canada, Mexico, Central and South America, the Caribbean and Bermuda.
And starting January of next year (2008), U.S. citizens who travel by land or sea will be required to show a passport when traveling between the U.S. and Canada, Mexico, Central and South America, the Caribbean, and Bermuda.
Yes, even students who go south of the border for spring break will be affected!
Note though that the following are NOT foreign countries, but US territories. You do not need a passport for traveling to these places: