Websites
These websites list vegetarian and veg-friendly restaurants. Some also offer natural food store listings and travel resources.

The Vegetarian Resource Group's Online Restaurant Guide is a searchable web version of their book, Vegetarian Journal's Guide to Natural Foods Restaurants in the U.S. and Canada.

VegDining.com sells a VegDining discount card and a
VegDining.com account with added featues for subscribers, including travel resources.

Happy Cow's Vegetarian Guide to Restaurants and Natural Food Stores offers many other resources as well, including travel resources, a forum and a bookstore.

Vegetarian-Restaurants.net also lists
natural food stores and some fast food chains with vegetarian options.

VegGuide.org claims to be "The ultimate restaurant and
shopping guide for vegetarians and vegans."

Books
Vegetarian Journal's Guide to Natural Foods Restaurants in the U.S. and Canada (Paperback)
448 pages, includes information of special interest to travelers.

Healthy Highways: The Traveler's Guide to Healthy Eating (Paperback)
From the book description: "Over 1,900 natural food stores plus vegetarian and health-conscious restaurants throughout the USA....MOST IMPORTANT -- each listing is keyed to state maps, along with local driving directions."