Advisories and Documents

FAA Flight Delay Information

Flight Arrivals, Departures, Delays and Cancellations

FlightAware

National Traffic and Road Closure Information

Passport Services
Smart Traveler Enrollment Program (STEP) - State Dept.

Transportation Security Administration - Advice for Travelers      

Travel Warnings and Consular Information Sheets   

Visa List

Airfare, Online Ticketing and more

Airfarewatchdog

Expedia

Hipmunk

Google Flights

Kayak

Momondo
Orbitz

Skiplagged
Travelocity

TripAdvisor

Yahoo! Travel

Airlines

Airline Toll-free Numbers and Websites

SeatGuru: Airplane seating information, etc.

Books and Guides

America's Byways

Atlas Obscura

Fodor's
Frommer's
Let's Go
Lonely Planet

Road Trip USA
Roadside America
Rough Guides

Trip Historic

Wikivoyage

Cruise sites

Cruise Compete

Currency Converters

General Travel Sites

CNN Travel

National Geographic Travel

New York Times Travel

Smithsonian Magazine Travel

Travel and Leisure

U.S. News & World Report Travel

Health

Shoreland's Travel Health Online
Travelers' Health -- Centers for Disease Control and Prevention

Hiking/Camping

AllTrails

Backpacker
Camping

Trails.com

Woodall’s North American Campground Directory 

Lodging

AirBNB

Bed and Breakfast Inns Online

BedandBreakfast.com

HomeAway

Hotels

Hostels: Hostels.com and Hostelling International

Trivago

VRBO Vacation Rentals by Owner

Parks and Recreation

Federal Parks

Federal Lands

The Hidden Worlds of the National Parks - Follow rangers on a journey to places most people never go

National Park Service

State Parks

America's State Parks

Florida State Parks

Park Search: United States via L.L. Bean

International

BBC Travel National parks around the globe

Parks Canada

Phrasebooks, etc.

TRAVLANG: Travel and Language

Railroad Travel

Amtrak

European Rail Schedule

Travel Deals

TravelZoo

Travel Tips

Country Insights: Centre for Intercultural Learning

Culture Crossing: A guide to cross-cultural etiquette