http://dictionary.reference.com/ A dictionary resource that also has a thesaurus and can translate words into different languages. http://www.merriam-webster.com/ In addition to definitions, this site also provides a word of the day and a variety of beneficial word games and crossword puzzles. Games include Syn City, Dictionary Devil, Up and Down Words, and Jumble. Finally, this dictionary can provide the pronunciation of words, a thesaurus, a visual dictionary and an encyclopedia. http://www.yourdictionary.com/ This dictionary search gives you definitions, thesaurus entries, spelling, pronunciation, and etymology results for your word. You can also browse the English dictionary alphabetically or by related terms to find meanings and synonyms. http://visual.merriam-webster.com/
Over 6000 images organized into 15 themes will allow you to connect a word with an image. This site is great for visual learners. It allows you to look up words to find their meanings and associations with other words and concepts.
http://thesaurus.reference.com/ Entering a word on this site will get you a definition along with a list of synonyms and antonyms from Roget's II.