Those of you who already are users of the popular “What the Font?” online service and happy owners of an iPhone will be happy to hear that the service has its own iPhone app now.
After installing it, you just need to take a picture of the font you want to identify, crop it, specify what characters are appearing on the image and get the results to find the closest font to match your image.
This is the best iPhone app so far for my taste, and would come really handy when wandering the streets looking for typography.