North American Bluebird Society (NABS)
The North American Bluebird Society serves as a clearinghouse for ideas, research, management, and education on behalf of all bluebirds and other native cavity-nesting species. NCBS (North Carolina Bluebird Society) is an affiliate of NABS.
http://www.nabluebirdsociety.org

Cornell Lab of Ornithology (CLO)
The Lab is a nonprofit membership institution whose mission is to interpret and conserve the earth's biological diversity through research, education, and citizen science focused on birds. One of the Citizen Science projects sponsored by CLO is The Birdhouse Network (TBN) in which participants gather nest box information such as the number of eggs and young in the nest, then submit their data over the Internet to scientists at CLO.

Cornell Lab of Ornithology: http://www.birds.cornell.edu
The Birdhouse Network: http://www.birds.cornell.edu/birdhouse/

Eastern Bluebird Rescue Group
http://www.easternbluebirdrescuegroup.org/index.htm

Virginia Bluebird Society
http://www.virginiabluebirds.org/

Other Bluebird Sites
You may be interested in visiting the web sites of the following organizations dedicated to the other species of bluebirds.

Mountain Bluebirds:   http://www.mountainbluebirdtrails.com/

Western Bluebirds:  http://www.prescottbluebird.com/