http://dictionary.cambridge.org/ Cambridge Learners' Dictionary]This has to be the best online dictionary available. It provides examples of usage from the corpus, all words derived from any root words that you enter, collocations and set phrases, pronunciation (IPA), differences between American, British and Australian usage and many other features.

http://www.merriam-webster.com/ Another good online dictionary as it has audio files of all words.

http://www.languageguide.org/english/ Visual dictionary. Choose a theme or topic, then scroll over the images with the mouse to see the names of items and hear the pronunciation.

American Heritage English Usage Guide Online

http://www.quickanddirtytips.com/GrammarGirl/EpisodeList.aspx Podcasts on improving your writing.

http://quibblo.com/ Build online quizzes that give students instant feedback. Free but subscription is required.

Cantonese Language Centre - English to Cantonese audio dictionary.

Lingro - A website that allows you to view English, Spanish, French, Italian and German webpages and click on text for translations or definitions.

Popjisyo - A website that allows you to read Chinese, Korean and Japanese webpages and scroll over text for English translations and pronunciation.

http://www.infovisual.info/ Picture dictionary

http://en.wikipedia.org/wiki/IPA_chart_for_English Pronunciation - IPA Phonetic Symbol Chart for English

http://www.dictionary.com Online Dictionary

http://www.thesaurus.com Online Thesaurus

http://www.onelook.com/reverse-dictionary.shtml Reverse Dictionary] If a word is 'on the tip of your tongue', type in a definition and this programme will give you possible words to fit it.

http://www.visuwords.com/ Visuwords Online graphical dictionary/ thesaurus. Enter a word and see it in the context of a neural network of associated words.

http://www.drgrammar.org/faqs/ Dr Grammar Frequently asked grammar and usage questions.

http://www.rhymezone.com/ Online Rhyming Dictionary]

http://idioms.thefreedictionary.com/ Idioms] Dictionary of idioms with examples of usage in context from literary works.

http://www.wordorigins.org Word Origins] A site explaining the origins of idioms.

http://www.krysstal.com/wordname.html Wordname] Origins of words and names.

http://dictionary.reference.com/translate/text.html Online Instant Translator]

http://www.wsu.edu/~brians/errors/ Common Errors]

http://www.bbc.co.uk/news BBC News]

http://www.scmp.com The South China Morning Post]

http://www.crossword-dictionary.com Crossword Dictionary ]Use it to search for words with the same sequence of letters.

http://puzzle-maker.com Puzzlemaker- build your own printable crossword puzzles.

http://http://linguistlist.org/ Linguist List: Includes "ask a linguist" discussion board.