WhatTheFont: recognize the font [AppStore, Free]

WhatTheFont is a popular Web-based tool to aid in identifying unknown fonts. Users can upload screenshots of text and get the list of possible used fonts.

MyFonts has now released a free iPhone version of WhatTheFont (AppStore link), allowing users to take a photo directly from the app using the iPhone's built-in camera and upload it to the WhatTheFont database for identification. It requires an Internet connection in order to analyze the image and access the font database.

via macrumors