If you travel on your own, then a printed guidebook is mandatory. The established companies have been around for a very long time: Michelin, Frommers, Fodors, and Lonely Planet. The merger of Exxon and Mobil pushed the Mobil guides online. They each have their advocates and detractors. It often depends on whether you prefer more detailed information and maps or like a compact format that is easier to carry. Frommers and Fodors follow similar book formats, and Lonely Planet and DK Eyewitness have a more compact and colorful format. Although you may get a better price online, I recommend browsing through a bookstore and flipping through the books and actually holding them in your hand.
Although the American Automobile Association (AAA) heavily promotes their road-side service, I find that their tourbooks, triptics, and maps are well worth the dues, and they’re free except for foreign countries. The Smithsonian publishes guides to Natural America and Historic America. In addition to the PBS series on television that are also available on VHS and DVD, Rick Steves publishes a series of guidebooks on European countries. The Insiders Guides publishes a series of regional guidebooks with local authors that are very comprehensive. DK Eyewitness Travel publishes a series of European city guidebooks that are very compact and have full color photos. The Rough Guide Travel Guides cover a lot of countries the others don’t. The Lonely Planet Travel Guides focus on economy travel.
Then there are specialty guidebooks that focus on specific interests, such as wineries. Amazon lists about 60 local relatively current guidebooks to wineries, and you probably can find one for your area in a local bookstore. Adventure travel is the latest wrinkle is specialty travel, and the GORP guides almost invented that category. Falcon Guides focus on hiking, camping, and biking. The web site trails.com catalogs outdoor recreation books by state into backpacking, camping, cycling, scenic, fishing, canoeing, birding, rock climbing, and skiing books and provides online access to sections of these books as well as links of how to order the books. The Poor Richard Web Press Bookstore web site has links to all of the guidebook publishers with direct links to order their books on Amazon.com.
http://www.insighttravelguides.com/catalog/formats_and_examples.php
http://shop.nationalgeographic.com/jump.jsp?itemType=CATEGORY&itemID=188
http://bookstore.prwp.com/section/Books/isle/17055/sub/Guidebook_Series
http://shop.lonelyplanet.com/index.jsp
http://mobiltravelguide.howstuffworks.com/
http://gorp.away.com/gorp/location/main.htm
http://www.trails.com/catalog_category.asp?categoryid=10087
http://us.dk.com/static/cs/us/11/travel/intro.html