Mango Languages offers a paid online language learning platform with lessons and courses for learning a growing number of languages. At the time this article is going up online, these include Brazilian Portuguese, English for Polish speakers, English for Spanish speakers, French, German, Greek, Italian, Japanese, Mandarin Chinese, Pig Latin!, Russian and Spanish.
The lessons are organized, friendly to the eyes, useful (from a language-acquisition perspective), colorful, feature-rich and are comprised of large amounts of quality learning materials including color-coded text and audio, which allows the learner to hear and see the target language simultaneously.
With the active Mango Team working hard on their next steps, Mango Languages will surely continue developing actively.
Update on 2012-11-26: Mango now offers apps for mobile devices including iPhone, iPad, iPod Touch and Android. Like the web platform, these apps provide great features (see below).
The apps are free to download and sync with your paid Mango account to keep all your learning materials available in one place.