Let me tell you Duolingo is free, completely free, really free.
By comparison, one box of the famous Rosetta Stone can easily cost you hundreds of dollars. But the fact the online Duolingo learning tool is free shouldn't be the only reason entice you to give it a try. In fact, the low entry barrier in pricing is very attractive, the main reason I'm recommending it is because of its quality, college level quality. Polyglot Benny Lewis of Fluent in 3 Months once said Duolingo is addictive per his experience, which shows how good Duolingo is.
Duolingo is scientifically proven. The founder Luis von Ahn is the same guy behind the idea of CAPTCHA. The extended idea of CAPTCHA has been built into Duolingo. Such idea is to crowd source the task of translating some websites from one language into another, and to have people learn a second language and help translating the website at the same time. Wonderful thought.
Duolingo comes with mobile app version too. Its mobile app is available for both Android and iOS. You can get them here.
Today, you're able to learn languages for free. You're able to do this online. You can do this at your own pace.