America's Guide to Speaking British.
Over 1000 words and expressions that differ in their usage between the US and the UK.

American Sign Language.

Applied Language Solutions.
Get text, e-mail, or website translations for Arabic, Chinese, Dutch, French, German, Italian, Japanese, Korean, Portuguese, Russian, or Spanish.

AskOxford.com.
A site to answer most of your language questions. Includes such things as a Collective Terms site, where you can find out what to call a group of swordfish, gnats or other animals; a Frequently Asked Questions site that answers questions on grammar, symbols, word origins, and other things; advice on better writing, word games, and more.

Cherokee -- Raven's Tsalagi Resources.
Contains the Cherokee Syllabary created by Sequoia (aka George Guess), a lexicon of most requested words, and more.

Dictionaries.

English As A Second Language.

Ethnologue.com.
Lists the majority of the languages known in the world by country.

Forvo Pronunciation Guide.
All the words in the world pronounced by native speakers. If you wish, you can also record a pronunciation for others to hear.

Greek and Latin Language Resources.
Links to dictionaries, grammars, tutorials, and more.

Languages - from the BBC.
This site includes many resources for learning French, German, Spanish, Italian, Greek, Portuguese, and Chinese.

Learn Japanese.
Includes links to several self-learning resources as well as instructions on how to install Japanese on Windows.

Learn Spanish.
A free online tutorial, including cultural notes.

VisualLinkLanguages.com.
Learn Spanish, Italian, French, German, Russian, Japanese, Chinese, and English (for native French speakers). Standard greetings, verb conjugations, weekly video lessons and more.

Web of On-Line Grammars.
This site maintains links with on-line grammars, including reference grammars, learning grammars, and historical grammars. Languages include Akkadian, Bengali, Cree, Danish, Dutch, English, French, German, Greek, Hebrew, Hungarian, Italian, Latin, Quechua, Russian, Samoan, Seneca, Spanish, Swahili, Swedish, and Welsh. Claims to limit links "to those grammars which are accurate and useful for learning the language they describe."

Wilton's Word & Phrase Origins.
Includes a list of over 270 words and phrase origins, as well as special topics such as, "how many words are in the English language?" loan-words and where they come from, common errors in etymology, and more.

Yamada Language Guides.
From the University of Oregon, this site is a definitive guide to language resources on the World Wide Web.