ADVENTURE Search through 3,000 trips (from biking to safaris) by date, price, and region at iExplore.com.
AIRLINE SEATS Seatguru.com maps out the best and worst seats, by jet type, on six major U.S. airlines.
AIRPORTS For details on terminals and transportation at nearly 200 airports, go to Worldtravelguide.net.
ECOTOURISM Find links to lodgings, tour operators, and travel services at Ecotourism.org/travelchoice.
ELECTRIC AND PHONE ADAPTERS Check Kropla.com to find out which plugs you'll need where.
EUROPEAN AIRFARES Applefares.com quickly searches two dozen budget airlines for travel within Europe.
EUROPEAN TRAINS For interactive route maps and point-to-point and rail-pass tickets, head to Raileurope.com.
HEALTH CLUBS Healthclubs.com helps you locate 5,400 gyms in 64 countries by address and features.
INTERNET CAFÉS At Cybercaptive.com, search among more than 6,000 cybercafés by state, city, or country (though, unfortunately, not by address).
LOYALTY PROGRAMS Manage accounts and learn all about air, hotel, and car-rental programs on Webflyer.com.
MAPS The clearest directions, including turn-by-turn maps, for North America and Europe are at Mapquest.com.
SEARCH AIDS Download Sidestep.com's program, which searches dozens of air, hotel, and car-rental sites and compares their rates with suppliers such as Expedia and Travelocity.
SPAS Spafinder.com has details about and special deals for day, hotel, and destination spas.