Learning a new language can be useful for business, a foreign vacation or as a fun hobby, while learning about a different culture and our own language in the process.

But if you're not an enrolled student, in high school or college, the best options you usually have are phrasebooks or Berlitz tapes.

Zach White

The computer program Rosetta Stone has dominated the independent language-learning world in recent years, but their software packages cost hundreds of dollars — cheaper than a college course or tutor but still a relatively large sum.

Guatemalan computer scientist Luis von Ahn h...