English Gaelic Dictionary This dictionary allows you to translate from English <> Gaelic. It doesn't have definitions or examples of the words, but does have flash cards and synonyms.
English Gaelic Tutor This is an English/Gaelic word matching game that helps build Gaelic vocabulary. Simple, but effective.
uTalk Scottish Gaelic This is a great learning app and costs $9.6. It has a variety of learning tools and makes use of pictures and quizzes and fun games. Can't store on SD card. :(
Learn English Gaelic This is an Engligh Gaelic flash card and word matching app. Easy to use, but kind of limited.
MultiLing Keyboard This keyboard has multiple languages (including Gaelic) and layouts for them built in. It also has many different kinds of predictive text, and tons of great features. Very useful! Multipurpose.