Below you'll find information about passports, visas, health warnings and country specific information provided by official government sites in the US and UK. Sometimes not knowing can ruin your trip.

Resources & Requirements (US Citizens)
Visa & Passports
Travel Advisories by Country
Travelers Health Information, from the CDC
Do I need a Visa?, Foriegn entry requirements
U.S. Customs - Traveler Information
U.S. State Dept. - Services, passport agencies, doctors and hospitals abroad, tips for American students abroad, travel publications and much more.
U.S. Embassies and Consulates Worldwide, hyperlink directory

Basic, Country Specific Information
Library of Congress Country Studies, 101 countries are profiled with the exception of Canada, France, the United Kingdom and other Western nations, and a number of African nations. Presentation is crude, text on gray background, but information includes analysis of the historical setting and the social, economic, political, and national security systems and institutions of countries. Search or browse.
CIA - The World Factbook - Country Listings, just the facts, but a whole new look. Maps, geography, people, gov't, economy, communications, transportation, military and transnational issues.
UK Foreign & Commonwealth Office - Travel Advice, totally redesigned, spiffy site with a pulldown menu for country travel advice.

Travel Essentials & Services
Currency Converter, exchange rates, dollar to whatever.
World Travel Insurance
Weather Information, international, travel, maps, more.