General Sites
English Language Center Study Zone (some good reading, grammar, and vocabulary exercises)
BBC World Service: English Language Learning and Teaching (news and English lessons on science and technology - a very good reading and listening site)
The English Zone (an excellent site that has grammar, idioms, spelling, vocabulary, reading, and writing exercises - Unfortunately, to get access to all parts of this site, there is a membership charge of US$30/year)
Grammar
English Works! Grammar (a wonderful source for good grammar explanations and lots of exercises)
Grammar Bytes (an excellent site for grammar terms, rules, exercises)
Big Dog's Grammar (basic English grammar with some good interactive exercises)
Guide To Grammar and Writing (the level is a little high but this is a very complete guide to grammar and it has some simple PowerPoint presentations for some grammar points)
The English Zone (an excellent site for grammar)
"The Ten" (The Ten Most Common grammar errors in writing)
Listening
Language Guide.org (a very cool dictionary with excellent North American pronunciation)
Authentic American Pronunciation (good clear examples of days, months, numbers, etc.. - no exercises)
Randall's ESL Cyber Listening Lab (good listening exercises - easy to difficult - many dialogues)
Takako's Great Adventure (ten episodes of a mystery with listening exercises)
CLA Interactive Listening Exercises (very simple word and phrase level exercises)
TPR Exercises (simple action related vocabulary - listen and select picture)
Learning Oral English Online (good clear carefully scripted dialogues - no exercises)
HKUST: Self-Access Center (excellent dialogues full of pauses and redundancy - no exercises)
The English Listening Lounge (the New Listener Menu has easy listening activities - monologues)
Focus English (good dialogues for common activities with exercises)
ABC Asia Pacific: Living English (some very good video clips with exercises - everyday activities - Australian)
OM (Audio, Listening, Bus - good conversation; Detective stories; Smiles - humorous stories - with exercises)
BBC: Learning English (short, clear monologues - British)
Literacy Network Learning Resources (TV news stories with video, listening, scripts - try the Story of the Week or the Story Archives)
English Language Listening Lab Online (Many short talks on a wide range of topics in a wide variety of accents. Allows listening with pictures, quizzes, and transcripts. Oral questions included.)
Numbers (basic pronunciation of numbers - one simple quiz)
- Numbers Comprehension (basic numbers quiz)
Reading
Talesetc.com (stories for children and adults - excellent reading - no exercises)
The Why Files (interesting and fun articles on the science behind news stories)
Literacy Network Learning Resources (TV news stories with scripts - try the Story of the Week or the Story Archives)
Pronunciation
Phonetics: The Sounds of American English (Some very cool animations and video explaining how consonants are spoken)
English Pronunciation (QuickTime movies showing sounds being made; good minimal pairs practice; the dictation practice is very difficult. Lessons on mp3 and PDF available - Okanagan University College in Canada)
American English Pronuciation (This site deals with many problematic areas and sound combinations; good quizzes)
Sounds of English (Good ideas for teachers)
Spelling
Basic Spelling Rules (some good practice exercises)
Spellzone - Learning Tips (good information about how to improve your spelling. Spellzone has a spelling course that you can pay for.)
Idioms and Slang
Urban Dictionary (a slang dictionary that anyone can add to)
The Online Slang Dictionary - A Collaborative Project (This site is updated regularly. Slang is submitted by anyone who wants to participate.)
Wayne Magnuson English Idioms: Sayings and Slang (This is an excellent site with good search ability if you know the idiom or just some of the words.)
Slangsite.com (another good, easily searchable site that includes slang, webspeak, made-up words, and colloquialisms)
A Dictionary of Slang (for those who need British English slang)
Peak English: Slang of the Day (includes sound file)
Other Useful Sites
Enchanted Learning (This is one of the most interesting sites I've ever seen. It has interesting reading on science topics: e.g. whales, deserts, oceans, biomes. The reading level is intermediate and there are hyperlinks to a good dictionary and lots of pictures.)
How Stuff Works (lots of information about almost everything - The language is fairly easy and there are lots of pictures)
Dictionaries
Oxford Advanced Learner's Dictionary (one of the best learner's dictionaries on-line; definitions are easy to understand)
Encarta World English Dictionary (an excellent dictionary with a speaker link that says the words and has a pronunciation key that also says all of the English sounds)
All Words Dictionary (definitions are easy to understand, gives pronunciation)
yourDictionary.com (an excellent dictionary with a speaker link that says the word)
Merriam-Webster Dictionary (definitions and thesaurus - very fast - sound)
Dictionary.com (and excellent dictionary and thesaurus, also games)
Longman Dictionary of Contemporary English
Cambridge Learner's Dictionary
Search Engines
Google (excellent - my favorite)
AltaVista (very powerful)
Yahoo (powerful and very good for finding strings of text)
Ask (easy to use because you can write questions as you normally would)