I just found this on iPhone App Store. It is a free download. Has anyone else used it? http://leafsnap.com
Sounds interesting. I've tried out a couple other ID apps, but they were almost worthless, because they didn't really give that great of assistance finding the right item. You basically just had to thumb through their rather limited collection, given only a couple limiting factors, like general leaf arrangement. Would be nice to be able to just snap a pic and find the right one. If you live in the Northeast, I highly recommend "Trees of the Northern United States and Canada" by John Laird Farrar. It's pretty complete, with pics of the leaves, bark, flowers, and fruit, and descriptions of them and how they vary between closely related species, like red vs sugar maple, etc. If you don't live in the northeast, the best thing IMO is to find a book and just look around and ID your local trees. Once you've cut a lot of them, you can start to tell just by the look of the wood grain, or by the smell. Highly useful knowledge for when you run across some dead, barkless trees in the woods, or roadside scrounges where you can't find any leaves.
I typically have the need to ID a tree without leaves. I tested the app last night. Out of 180 trees on file after taking a picture it could narrow it down to 10 for you to choose from. The best part was the image library. You could view the buds, flower, fruit, seeds and bark.
the one i like to use is Virginia Tech tree id. Very large amount of trees and works fairly well so long as you know some characteristics about the tree/leaf
