If it supports the language your're looking for, Duolingo is a great option. I know it's probably not the best or most advanced teaching (but it's pretty damn good), but the two main benefits are:

A: It's free. Install and start with no payments needed. Having to get out the card and debate the payment stops a lot of people cold.

B: It nags you all the time. Keep your streak going! If you don't practice every day, you're going to hear about it. You'll make the cartoon owl sad. It becomes an addictive game, how long can you keep your streak going?

The main benefit of this is that you actually use it. Actually learning every day, even without the best materials, is FAR better than having the best materials and rarely using them.

Good luck!