iOS: Udacity is already well known for hosting free, useful online classes in a range of topics, including robotics, computer science and mobile development. Now, the Udacity app for iPhone and iPad lets you take those classes with you for free.
The new app essentially serves as a mobile portal to all of your subscribed or available Udacity courses. You can use the app to sign up, see what's available and interesting, see what the requirements for the class are, and whether a certificate will be awarded when you finish the course. Any videos associated with your course are available to view on your phone or tablet, and you can download them for use offline if you know you'll be travelling without an internet connection.
The app is completely free, and it's available now. If you're interested in more classes like the ones offered by Udacity, check out our Lifehacker U series, which is packed with free online classes from Udacity and other institutions.
Udacity (free) [iTunes App Store]