•  American Heritage Dictionary, 4th Edition
•  Biographical Dictionary 
  Over 28,000 notable men & women who shaped
  our world to the present day.
•  Cambridge Dictionaries Online 
  this dictionary shows how to use the words in
  sentences (good for prepositions)
•  Dictionaries  various languages
•  Dictionaries in the Yahoo! Directory    dictionaries,
   foreign language, slang, thesauri, and more...
•  Dictionary.com:   Free online English dictionary,
    thesaurus, reference guide, crossword puzzles 
   and other word games, online translator and
   Word of the Day.
•  Encarta dictionary provides a pronunciation guide!
•  Macquarie Dictionary (Australian)
•  Merriam-Webster's Collegiate Dictionary  (Unabridged)  This has a larger number of words in it than many online dictionaries...   
•  Microsoft Encarta World English Dictionary
• One Look Dictionaries Look up a word or term in lots of dictionaries!  (and glossaries)  Access to a frequently  
  updated database of words, terms, names, and acronyms
•  One Look's Reverse Dictionary  lets you describe a concept and get back a list of words and phrases related to that concept.   www.onelook.com/reverse-dictionary.shtml
•  Oxford English Dictionary, 2nd Edition
•  Random House Webster's Unabridged Dictionary
• The Wordsmyth Dictionary-Thesaurus home
   this dictionary provides specific definitions of word forms.
•  V2 Vocabulary Building Dictionary  This is an important new resource.  One of the ugliest dictionaries I have ever seen and filled with horrible advertising.  BUT.... the resources in the center of the page are some of the best dictionary resources online.   
•  Your Dictionary.com  Authoritative portal with 2500
    dictionaries, grammars, 300 languages, games and more.
   
  Concordance sites
  A Concordance program is a computer program
  that can help you analyze the language used in
  real situations. You can use these programs for free.

     DirPedia.com
      a dictionary, encyclopedia & web directory
      http://www.dirpedia.com/

• Encyclopedia:  
• World Book Encyclopedia
• More Encyclopedias and Dictionaries
• Encyclopedia

for what you need!     
Here's a good place to begin!   

•  Acronyma
•  Acronym Finder  what abbreviations mean.
   Ask Oxford
•  Barrel Full of Words
•  Bill Casselman: Books, Words & Language
•  Collins Word Exchange
•  Crossword Puzzle
•  Isms

•  List of Dictionaries  Paderborn, Germany

•  One Letter Words
•  Online Dictionaries and Translators
•  Philosophical Isms at Phrontistery:
   
  • Word Finding Tips
     - how to find a word you're looking for quickly and easily
  • Numbers and Numerical Prefixes
    - a discussion of numerical prefixes in English
  • 2 and 3-Letter Scrabble Words
    - complete American and international lists
  • Linguistic Disquisitions
    - essays and rants relating to English words and language use
  • Forthright's Favourite Words
    - 50 of my favourite unusual words described in detail
  • English Language Resources and Links - other sites of interest to word-lovers
•  Richard Lederer's Home Page
•  Scrabble FAQ
•  The Devil's Dictionary
•  The Word Wizard
•  Visual Thesaurus
•  Word puzzles from syndicate.com
•  Wordsmyth - Dictionary&Thesaurus
•  

        Quotations

•  Bartlett's Familiar Quotations  
   A collection of passages, phrases, & proverbs.
• Dictionary of Quotations
• WritingResource.org: Quotations
   
  Thesauri

• A random word from the archives
• A.Word.A.Day: the newsletter, the book
  discover the magic of words
• Another Word A Day
  the new book - more fun with words
• Wordlovers' Library Project
  free books for libraries worldwide
• Internet Anagram Server
  find the wisdom of anagrams
• The Wordserver
  lookup services via email
• Listat
  a statistical tool for mailing lists