Here are some general apps that can be helpful when you're on the go. Beware that many require Internet access and that may or may not be available.
Figure out which language you want to learn/practice and then check out these popular series of language-learning tools. Some are books, some are software, and the bar charts look just like sparknotes, except for languages. The bar charts are one of my faves because they're so easy to carry around on your trip.