The Pammac English Catalan dictionary is the best ever two-language dictionary on the iPhone/iPod Touch.
It contains more than 33.000 words and expressions and they are available right on your hands. You dont need to be connected to the internet: no 3G or WIFI needed at all. Just search, find and learn! It will work even in the North Pole.
This App is licensed under the GPL v2 license and is based on the Dacco project.