OLPC is working in many countries and languages. Language learning, particularly of major world languages, is a common need for early education. The XO holds the promise to make language learning accessible to many for the first time. See also Literacy.
For more basic skills training, including literacy and ESL, see the discussion at Avallain.
Colingo, a web-based language learning nonprofit, is working to create free ESL videos and other materials for OLPC.
Friendly Language is working on developing free language learning material in as many languages as possible for the XO, and is also working on tools for language learning, such as multilingual instant messaging.
Other language learning tools
The Blue Book of Grammar; online quizzes and guidebook (English).
www.livemocha.com LiveMocha is a free online language-learning program.