Information about study abroad
http://globaled.us

Bureau of Consular Affairs, US Department of State
http://www.travel.state.gov

Travel Warnings/Public Announcements/Consular Information sheets
http://www.travel.state.gov

Tips for US Students Abroad
http://www.travel.state.gov/travel/living/studying/studying_1238.html

Links to US Embassies and Consulates Worldwide
http://www.travel.state.gov/travel/tips/embassies/embassies_1214.html

Centers for Disease Control and Prevention
http://www.cdc.gov

Traveler's Health
http://www.cdc.gov/travel

Association for Safe International Travel
http://www.asirt.org

SAFETI Project Website at the University of Southern California
http://www.globaled.us/

U.S. Passport Service
http://www.travel.state.gov/passport/passport_1738.html

International Student Identification Card (ISIC)
http://www.counciltravel.com/idcards/

Airlines:
http://www.statravel.com
http://www.studentuniverse.com/fly/main
http://www.cheapflights.com
http://www.easyjet.com 
http://www.ryanair.com (for flights within Europe)

Rail passes:
http://www.raileurope.com

Youth Hostels:
http://www.hostelworld.com