These are some great websites about birding that are worthy of being mentioned.

http://www.birdingonthe.net/

This website has a mailing list that members can join. It also has information about birds all over the world. You just need to click the area that you are interested in.
http://www.its.caltech.edu/~feenstra/
Jonathan Feenstra walked with us when he was a graduate student at Caltech and he is an amazing bird watcher. He has set the record for most species seen in LA County in one year. Check out his site for the birds he has seen and photos.
http://www.astro.caltech.edu/~aam/
Ashish is a Research Scientist in Astronomy at Caltech and he also has an ornithology section on his personal website. You can also find a link to the weekly walks on his site which contains a lot of great data.
http://groups.yahoo.com/group/lacobirds/
LA County Birds Email List
http://www.PasadenaAudubon.org/index.html
Pasadena Audubon Society
http://www.esaudubon.org
Eastern Sierra Audubon Society
http://fog.ccsf.cc.ca.us/~jmorlan/county.htm
This website has everything you could possibly want to know about birding in California including links to all the email lists for all 58 California counties.
http://www.virtualbirder.com/
This interesting site allows one to, among other things, take a virtual bird walk at some interesting birding spots around the US.
http://www.hbw.com/ibc/phtml/whatIBC.phtml
This site allows one to, among other things, look at videos of birds from around the world.
http://www.bird-stamps.org
This site has all the stamps of the world that feature birds on them
http://www.birdtheme.org
This site also has all the stamps of the world that feature birds on them
http://www.laaudubon.org/
Los Angeles Audubon Society
Rare Bird Alert for LA County
Rare Bird Alert for Los Angeles County
http://www.birds.cornell.edu
Cornell bird website
http://pictopolis.blogspot.com
Paul Roa's Bird Blog
http://www.birdsource.org/gbbc/
GBBC homepage
http://gbbc.birdsource.org/gbbcApps/checklist
GBBC checklist page; has lots of bird info
http://ebird.org/content/ebird/
ebird.org webpage; take birding to the next level
http://www.robert-harrington.com/
Bird photos by Robert Harrington