Omniglot is an impressive guide to over 500 languages, including detailed information on over 180 different alphabets, syllabaries and other writing systems, with plenty of background information and written samples. It also includes useful phrases in a large number of languages, many with audio.
iLoveLanguages was an encyclopaedic set of links for a broad range of languages, but seems to have been neglected lately.
Loecsen Essentials have a good collection of basic words and phrases in over 40 languages, represented pictorially, with a quiz.
UCLA Language Materials Project has a database of bibliographic references for over 900 languages, which can be searched by type of material, level of instruction, whether audio is available etc., often with methodological information. There are also detailed profiles of over 100 of the languages.
Routledge's Colloquial series - good quality book+audio courses in 70 or so languages, with the audio component freely available on their website.
Live Lingua Project collects together major public domain language learning materials, including the FSI Language Courses in many languages, developed by the US Department of State's Foreign Service Institute in the 1960s and 70s.
Less Commonly Taught Languages project, based at the University of Minnesota, focuses on where you can go for courses in your chosen language, though it also has some interesting royalty-free instructional materials.
SOAS Language Centre offers evening classes in many African and Asian languages.
They have a number of high quality online resources in a variety of languages.
ATLAS offers a good taster of many languages: Arabic, Czech, Danish, Dutch, Greek, Hebrew, Hindi, Lithuania, Mandarin, Polish, Portuguese, Russian, Swedish, Tigrinya, Turkish, Urdu and Yorùbá.
The CEELBAS Language Repository has open-access teaching and self-study materials for languages of Central and Eastern Europe and Russia, some specifically aimed at social sciences/humanities researchers. Languages include Bulgarian, Croatian, Czech, Estonian, Finnish, Georgian, Hungarian, Polish, Romanian, Russian, Serbian, Slovak and Ukrainian.
hayya bina (Let's go!) is a web-based course of Modern Standard Arabic for beginners, developed with EU funding by partners including the University of Exeter. Learners can study with Western script, with Arabic script, or with both; it's clearly presented, with plenty of audio (recording too), and users can even choose to study in different mother languages.
Madinah Arabic offers a reading course as well as a spoken language course.
Babel:arabic - basic lessons with sound, plus grammar lessons.
Scripts of All Asia shows characters and their corresponding sounds in many Brahmi, East and Southeast Asian languages.
Beginning Bambara (An Ka Bamanankan Kan Kalan), the major language of Mali - audio lessons from Indiana University, who also offer an intermediate course. See also Bambara 101 which takes a text-based approach.
Larry Trask's Basque Page - material by the late University of Sussex professor of Linguistics has been thoughtfully preserved at Buber's Basque Page which includes language-learning material and cultural background.
Survival Bengali provides an introduction to the language via a few lessons, phrases with audio and a small dictionary (from Virtual Bangladesh).
On-line Gaelic at the University of the Highlands and Islands has hundreds of classified links to pages in and about Scottish Gaelic and other related languages - there are plenty of links for Gaeilge (Irish Gaelic) there too.
Gaelic Homepage with lots of resources and links to further information on the three Gaelic languages.
galego.org - articles on the Galician language: its history, sociolinguistics, a small dictionary etc. In Galician, Spanish and English.
Introduction to Modern Greek leads you gently through learning the alphabet, numbers and basic grammar - includes audio and doesn't need Greek fonts installed.
Greek through the Internet - a series of lessons and drills, plus grammar and syntax to help you learn Modern Greek.
Hausa CALL is a multimedia introduction from SOAS, with exercises.
See also tutorials and references from Russell Schuh at UCLA.
Introduction to Korean - an excellent set of reassuringly easy-to-follow tutorials for beginners - includes audio and doesn't need Korean fonts installed.
Thai-language.com includes over 10,000 audio clips for learning Thai, alongside a bilingual dictionary of around 30,000 terms and a forum. The FAQ section is also full of tips for further study and using Thai on your computer.
Learning Practical Turkish offers an entertaining way to learn the language, with "Sounds of Specialty Turkish": business, computing and culinary terms, for example, and even tongue-twisters in RealAudio!
Read Ukrainian - well-designed supplementary materials for reading courses in Ukrainian.
Welsh Course from Cardiff University (though originally from Brown University), including dictionaries, a spellchecker and links to lots of other Welsh resources around the Internet.
Wolof online - comprehensive interactive course with samples and conversation snippets.
