I've just revamped my links section somewhat. I'll take that as an excuse to expand on some of the links in the "Reference" section.
Birdmail (aka "Siler's page") is probably known to every active birder. It provides a way to keep up with the birding mailing lists in places both near and far. There's even a section for those of us who've gotten distracted by bugs.
Searchable Ornithological Research Archive (SORA) has been an invaluable boon to this blog so far, and I don't expect that to change. Here you can search the back issues of ornithological journals such as the Auk, Wilson Bulletin, Condor, Western Birds and others. This is a terrific online resource because runs of these journals are not always easily found. Making them available online for the use of researchers is one of the things that adds value to the internet. I encourage every reader of this blog to visit SORA and explore the archives. You're sure to find some intriguing information there.
Ornithological Books Online is a collection of links to, well, ornithological books online. This page can lead you to John James Audubon and Alexander Wilson's works (although some of the links may be outdated). A good adjunct to this is the new Google book search, which has started adding some older (i.e., public domain) works in their entirety. Several of Frank M. Chapman's books, such as Handbook of Birds of Eastern North America and Bird-Lore, can be found at Google.
Finally, we have an edited version of Arthur C. Bent's Life Histories of North American Birds. Although some of this information has been superceded by more recent research, these vignettes often provide a vivid look at bird behavior. These accounts also provide a different model of scientific writing than we are accustomed to today; the reports that Bent quotes are almost chatty by modern standards.
I'm sure that the links section will grow in the future, but that's the "Reference" section for the moment.