Duolingo is the first language learning site I ever used and still do. The biggest advantage to it is that it is completely free.
It’s a spaced repetition program designed to make language learning a game and also has apps available for smart phones / tablets.
It starts off very simple and you have to complete sections to unlock others. You can set a daily goal and the app will send you notifications if you have forgotten to do your study for that day (handy if you are prone to forgetting like I am)
You earn “lingots” for completing sections and goals. These don’t unlock a great deal but do allow you to spend them on a couple of additional modules (“Idioms and Proverbs” and “Flirting”) or to take timed practice and progress quizzes.
It’s fantastic for learning the basics although I thoroughly doubt that you will get much beyond the beginner stages by using this alone. Coupled with some speaking practice, this is a very good tool.