Cornell Lab of Ornithology
http://www.birds.cornell.edu/

Patuxent Bird Identification InfoCenter
www.mbr-pwrc.usgs.gov/id/framlst/infocenter.html

Lehigh Valley Audubon
www.lehigh.edu/~bcm0/lvas.html

Birdwatching
http://www.birdwatching.com/