Sign language is a visual language and so using an iPhone to learn works quite well. It's amazing how fast you can pick up simple signs when you can watch the sign being shown through illustration or video. Even parents are learning and teaching their babies how to sign using some of these sign language apps. Whether you want to learn sign language so you can communicate with someone who already uses the language, or just for interest's sake, check out our list of the best iPhone apps for learning sign language.