Arizona Office of Tourism (www.visitarizona.com) Comprehensive planning information, covering sights, activities, accommodations, current trends and more. It also has a useful app.
Arizona Department of Transportation (www.az511.gov) Statewide travel and traffic information, including precise journey times.
Arizona Hikers Guide (www.arizonahikersguide.com) Good resource that covers all the highlights.
Lonely Planet (www.lonelyplanet.com/usa/southwest/arizona) Destination information, hotel bookings, traveler forum and more.