I think italki is a powerful tool in order to learn languages as well as in order to make friends worldwide. But, it is not the only tool, of course. If we really want to learn languages, we must work also whit other tools, like enrolling to a language school, studying by ourselves, reading, listening, speaking as much as we can in the language we are learning, etc,etc, etc. Practicing makes perfection.
But I don't know any other website as good as italki. Do you?