I agree with ian, duolingo is amazing, memrise is good and if you want to learn specific vocabulary, Anki is very useful. On the other hand, if your level is already quiet high, I thing that you could read books, listen to radio podcasts and look at tv shows according to your interests.

I like Wlingua also for Spanish.  I use Duolingo for vocabulary practice.  Duolingo has a lot of mistakes in it. It does nothing to explain things and they just throw random words at you.  There isn't a set mode or theme.  

For memorization, Quizlet and Memrise are quite good. Memrise gets a slight nod if you're looking for pre-made materials. Quizlet has some nice features to help quiz what you've learned.

If you'd like to practice speaking, I'd be happy to help you develop a study plan.  Feel free to look at my teaching profile and class offerings and send me a message if you think I can help you.

Duolingo! It also launched a Korean course few days ago. I'm very excited about it!