U.S. Department of State

• Travel.state.gov offes tips and links to successful travel outside the US, including passport and visa information.
• Travel Warnings
• Consular Information Sheets provide information on health conditions or unusual situations travelers should be aware of before departure.
  
• Country Background Notes for general information about a destination

World Factbook from the Central Intelligence Agency

Traveler's Health from the Center for Disease Control includes vaccination, pest and water information. A part of this site, the Yellow Book is directed to health professionals, but may be of interest to the traveler.