OneAcross Puzzle Dictionary

OneAcross.com is a great website for crossword puzzle afficanados.

Wiktionary

Wiktionary contains over a million entries with English definitions from over 295 languages. It also includes a thesaurus, a rhyme guide, phrase books, etymologies, abbreviations and more.

Pseudodictionary

A fun site for made up words, pseudodictionary allows the submission of words for inclusion.

Artcyclopedia

Search or browse this art resource by artist's name, title of work, museum, historical period or movement. Artist must have work in a museum to be included.

OneLookDictionary

OneLook contains and index of 900 online dictionaries with over 5 million words.

TheFreeDictionary.com

Hosted by Farlex, TheFreeDictionary.com is very comprehensive and allows searching of general and subject dictionaries, including foreign language, thesauri and encyclopedias. Includes idioms and acronyms.

Dictionary.com

Dictionary.com is the largest and most trusted free dictionary on the web. Hosted by Ask.com, it contains a dictionary, thesaurus and even encyclopedia searching. Searches the Random House Unabridged Dictionary, American Heritage Dictionary of English Language, Merriam Webster's Revised Unabridged Dictionary and the American Heritage Dictionary of Idioms along with many more.

Etymology Dictionary

Etymology is the study of the history of words. This online resource contains explanations of what words meant in the past.