There are plenty of places online where you can get much more exhaustive lists of all of the following things; these are just some of my preferences.

Websites - In addition to the blogs listed on the right side of my homepage, these are some excellent online birding sources:
  • eBird -  Do you use eBird? If your answer is "No," stop reading this and go set up an account right now. Be a part of this growing, worldwide community of citizen scientists working together to create an incredible database of information on birds.
  • 10000birds - "Birding, nature, and the wide, wide world."
  • Surfbirds - Photos, trip reports, blogs, outstanding ID articles, and much more.
  • Xeno-Canto - A rapidly developing site with any and every imaginable bird call. This is a great venue to work on spectrogram recognition, which I keep telling myself I will do one of these days.
  • ABA Rare Facebook Page - This is quickly becoming one of the best ways to stay up to date on Rare Bird Alerts.
  • Illinois Birder's Forum - One of the most active online birding forums; always an interesting discussion happening.

Apps: carry these with you wherever you go!

  • BirdLog - This is an incredible tool that should be in the hand of every birder with a smartphone. It allows you to enter your checklists on the go, increasing your checklist accuracy. And the beauty of it is that once you get home, all your lists are already complete!
  • BirdsEye Hotspots - An excellent app replacing BirdLog NA, which was wonderful in it's own right; but at $4.99, how can you pass this up? If you've used BirdLog NA, here's the comparison with BirdsEye Hotspots.
  • iBird - This is Field Guide app that I use the most. It's so nice to be able to take it right into the field in your pocket. This is the only Field Guide app that combines illustrations (though some are better than others) and photos. Wait for a sale and you can get it for cheap.
  • Sibley Guide - From what I've seen of it, this looks to be the best Field Guide app out there. I don't have it personally because I don't want to fork over $20 for it, and I haven't hit one of it's sales yet.
  • birdJam - you can empty your pockets on a pre-loaded iPod, or just by one of their smaller, family-specific apps. I have the Warblers app and love it. My patient wife is pretty much used to hearing warbler calls resounding throughout the house come springtime; this app is to blame.
  • larkwire - A fun app that teaches you bird songs through learning activities. Use it when you're alone, use a pair of headphones, or get used to everyone looking at you like you're a moron.

Books: because as technologically advanced as we are, nothing can beat an actual book in your hands.

  • Sibley Guide - Obviously this is where we begin, with the best Field Guide in North America. Keep an eye out for the forthcoming Second Edition, which will be hitting the shelves in March of 2014!
  • National Geographic Guide - Another staple Field Guide.
  • Birds of Europe - Argued by some to be the best Field Guide in the world. As expansive in information as it is compact in size, this guide may not seem useful at first to the North American birder. However, there is much to be learned from the portions on shorebirds and jaegers; and, familiarity with foreign species is a great way to pick a vagrant out of a flock of common birds.
  • Sibley's Birding Basics - An indispensable work for birders of all stages.
  • Kaufman Field Guide to Advanced Birding - Offers great explanation of birding skills, as well as lengthy discussions on some of the key ID issues facing birders in the ABA area (peeps, jaegers, empidonax flycatchers, and much more).
  • The Shorebird Guide - This is undoubtedly the best book out there on shorebirds, with stunning photos and helpful descriptions of both plumage and behavioral tendencies.
  • Gulls of the Americas - This Peterson Reference Guide offers incredible plates on each cycle of every gull in the Americas. The introductory matter is outstanding as well and is requisite reading for those wanting to plunge into the foggy world of gull identification.
  • Seawatching: Eastern Waterbirds in Flight - This Peterson Reference Guide is a masterpiece and a wonderful tool for learning how to identify waterfowl and the like in flight. The photo of two Long-tailed Jaegers chasing an Ivory Gull is worth the price of the book in my opinion.