Live Lingua is a website that connects teachers with students much like like iTalki and Verbling. But where it is different is in it’s free learning materials. Live Lingua has sourced and catalogued a whole range of free, public domain language learning material – both texts and audio files – which users can download from the site. These materials are chiefly courses that have been used in U.S. overseas projects like the Peace Corps. As such, they’re tried-and-tested learning methods that have been employed in real-world settings to great effect.
But take into account that a fair bit of the material is quite old. The resources have been collected from decades of foreign language teaching in US military institutions. That doesn’t make it any less pedagogically sound, of course; but it does mean that the format might be a bit rougher that what you might be used to.