Dictionary.com - free online English dictionary, thesaurus and reference guide
www.dictionary.com

Webopedia - computer dictionary for computer and internet terms and definitions
www.webopedia.com

Your Dictionary - quick dictionary - thesaurus lookup
www.yourdictionary.com

Cambridge Dictionaries Online - from the Cambridge University Press
dictionary.cambridge.org

Law.com - a dictionary of legal terms and definitions
dictionary.law.com

Medical Dictionary Online - free online medical dictionary search engine
www.online-medical-dictionary.org

Acronym finder - find the meaning of thousands of acronyms and abbreviations
www.acronymfinder.com