iOS: You wouldn't think a dictionary app could actually be fun to use, but Terminology somehow manages to be just that. Now, the app has gone free alongside an update that cleans up the interface.
The biggest part of the update is the new interface, which makes it easy to look up words and research terms. You can also bookmark words and Terminology saves your searches so you can easily go back to terms you've searched for in the past. The app also adds in audio pronunciation, which is helpful for more complicated words you run into. Terminology is free with an in-app purchase of $US1.99 ($3) to remove the ads.
Terminology (Free/$US1.99 [$3]) [iTunes App Store]