Download the Free Merlin Bird ID App
Free, Instant Bird ID Help for 400 North American birds from Cornell Lab
Merlin draws upon more than 70 million observations from the eBird citizen-science project.
It customizes your list to the species you are most likely to have seen at your location and time of year.
For even more free ornithological resources, see the article A bird in the hand: Free online ornithological resources