I tried out Mango Languages with Brazilian Portuguese. I was able to get only lesson one, which included a lot of vocabulary, a couple of conversations, and some grammar. Unfortunately, as soon as it seemed to be getting interesting, I reached a ‘wall’ and the website asked me to pay to get more features. I checked out what these other features would be, and they seem very useful. They have voice comparisons where I could record my voice and then compare it to a native speaker. They have lots of cultural sections. They also have mobile apps so learners can learn on the go, wherever they may be. Overall, if this website offers the language you may be interested in learning (and they have many!), it may be worth trying out (it does claim to offer a full refund within 60 days).
For more self-study tools, please check out: http://languages.oberlin.edu/self-study-tools/