I'm surprised nobody has listed this app yet. I use it mostly for learning Japanese but from time to time I also use it for brushing up on my Spanish. I guess you can say it is kind of like Duolingo except you get to choose which course you would like to learn. There are points and you can share your progress on social networks as well. You can register online first (recommended) and then sync up the app on your mobile device. My favorite thing about Memrise is that there is more to learn than just languages, you really just need to see it for yourself. Oh and the courses are written by other users so you get a chance to learn slang and other things. Seriously, go and check it out! www.memrise.com