Check the full article for an overview of other apps including Leafsnap and (Amazon) SnapTell
Google Goggles, which appeared on Android phones in late 2009 and on the iPhone last year, is best at deciphering landmarks, text, book and DVD covers, artwork, logos, bar codes and wine labels. You start the app — it’s part of Google’s search app for the iPhone — and peer at the object through the camera lens. It takes a stab at identifying it.
I’ve found the app especially useful for comparison shopping. If you’re browsing through a bookstore, for instance, one quick snapshot of a book’s cover allows you to check the price on Amazon. It’s much faster than typing the title into a search bar. Same goes for photographing paintings or craft beer bottles.