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BBC Languages: archived but still great
Languages of the World
About the International Language Proficiency Scale
Omniglot encyclopedia of writing systems and languages
List of Free Online Language Courses
for languages that use different alphabets or writing systems, download the appropriate keyboard:
RhinoSpike is an online language learning community tool that lets users around the globe connect and exchange foreign language audio files. Get any foreign language text read aloud for you by a native speaker!
Pictorial Vocabulary Guides and Interactive Readings in a variety of languages
PARALLEL TEXTS ROM ENGLISH TO 55 DIFFERENT LANGUAGES
iLoveLanguages is a comprehensive catalog of language-related Internet resource
Read children's books in various languages
Lingopolo offers audio resources for learning several languages. It is committed to a free model, and as I write this it is offering lessons in Dutch, French, Japanese, Thai, and Pandunia (a constructed global language like Esperanto).
You Know the Drill
Voca, previously known as Vocatude, is a free vocabulary trainer for Windows and Linux.
anki flashcard software
Language Software Reviews
Create your own online with Quizlet
The InterActive Terminology for Europe dictionary will give you translation of words for specialized terminology.
Search for words in context to gauge their actual meaning with Linguee. Note for most European languages, and Japanese.