Business Dictionary: http://www.small-business-dictionary.org/
This Web Site provides definitions to 2,500 of the most commonly used terms encountered by the start-up entrepreneur, the small business person and the student of business theory. Thus, this Web Site provide a totally functional small business reference; a comprehensive instant-answer source to just about any problem or question concerning small business principles, practices and concepts.

Cambridge English Dictionary: http://dictionary.cambridge.org/default.asp?dict=a

Merrian Webster Online Dictionary: http://www.m-w.com
Merriam-Webster delivers the most up-to-date dictionary on the Web — now with new words.

One Look Dictionaries: http://www.onelook.com/ 681 online dictionaries indexed.

Oxford English Dictionary: http://dictionary.oed.com
It is a password site and you have to sign in before being able to look words up.

Word Central: http://www.wordcentral.com/
Word Central is the language site for kids.

Your Dictionary: http://www.yourdictionary.com/
YourDictionary.com allows you to access 1800 dictionaries in 230 languages. YourDictionary.com features Merriam-Webster's Collegiate Dictionary and Thesaurus as its preferred English language resource.