If you love free public domain language learning resources as much as I do, then check out the Peace Corps Language Courses Archive. Live Lingua has a large collection of Peace Corps manuals teaching languages ranging from Acholi to Zarma (over 100 languages are available!) and some also include audio resources in addition to the language manuals. If you have other PC manuals to share, please let Live Lingua know and they will add them to their site.
The Peace Corps does have their own Digital Library of Technical and Training Manuals if you are also interested in learning more about the work that PC Volunteers do. Although this library doesn’t seem to offer language courses, some of the manuals are written in French and Spanish so they can still be used as language learning resources.