My absolute favorite bird-related magazine is
Birding, from the American Birding Association. Between it and the
Winging It newsletter (each published bi-monthly), I feel the membership cost is worth it. And of course the money does help support their programs and such.
Also want to mention that a membership to the Cornell Lab of Ornithology, which includes their
Living Bird magazine is also very much worth it. The magazine is great, the Lab does alot of good work, and it's tax deductible
I also subscribe to each of the 3 "mainstream" US birding mags:
Birder's World,
Bird Watcher's Digest, and
WildBird. I enjoy each of them, but would have to say that Birder's World is my favorite of the three. I feel that it's slightly more geared toward non-backyard birders than the other two. Plus, I'd read anything that has regular columns by Pete Dunne, Kenn Kaufman, and David Sibley!
You may want to check out the websites for each one and see which you like best. I know Birder's World has a good many archived articles that you can read.
You can find some pretty good deal on subscriptions (<$20), but it can be tough to know which sites are legit. Just do a little bit of research on the site before you place your order. Speaking of which, I need to renew a couple of them...