Spanish is a very popular language to learn for its musical sound and widespread use, having over 400 million speakers in Spain and Latin America. This is a list of online opportunities to learn Spanish for free, and it will be updated as I become aware of more options.
Memrise – Memrise offers a wide variety of Spanish courses.
Destinos – A free introductory online Spanish course.
Wikiversity – Offers two completed courses in Spanish, which include a lot of information on the countries where Spanish is spoken and cultural information about the Spanish-speaking world.
FSI Language Courses – There are a number of FSI courses available. The Spanish Basic Course is one of FSI’s larger courses, consisting of four volumes.
Duolingo – Duolingo offers beginner’s Spanish amongst a large number of other languages.
SpanishPod101.com – The Spanish version of the French podcasts discussed here.