A vast body of reference material is freely available online and can be accessed via Safari on the iPhone or iPod touch. Unfortunately, a lot of this material is optimized for desktop computers and is poorly suited to the iPhone’s smaller display and simplified user interface.
Fortunately, reference applications are popular, currently accounting for over 1,300 of the programs listed in the Apps Store. Some of these require an Internet connection, but many are standalone apps that are installed with the data you need. Among these titles you’ll find traditional dictionaries, religious references, language translators, medical references, formula lists, food and drink databases, and much more.
This article reviews, in no particular order, a few of the reference titles I found most impressive. All are available for the iPhone or iPod touch running verson 2.0 or later of the OS.