http://www.americanbirding.org
2. National Audubon Society
http://www.audubon.org
3. Birdwatching Dot Com
http://www.birdwatching.com
4. Bird Watcher's Digest
http://www.birdwatchersdigest.com
5. Peterson Online
http://www.petersononline.com
6. The Nest Box
http://www.nestbox.com
7. The Virtual Birder
http://www.virtualbirder.com
8. field guides
http://www.fieldguides.com
9. BirdSource
http://www.cornell.edu
10. Cornell Laboratory of Ornithology
http://www.cornell.edu