Merriam-Webster Visual Dictionary Online

Merriam-Webster's Visual Dictionary Online has 6,000 images and over 20,000 terms and definitions that are divided into themes.  Users can browse through the 15 themes or search for terms or images.  Some images are of individual terms and others are detailed diagrams.  This is great tool to help understand complex definitions and to explain the mechanics of different objects.

Thinkmap Visual Thesaurus & VocabGrabber.

Visual Thesaurus is another web tool that shows dictionary and thesaurus entries graphically in a web format.  Visual Thesaurus is a paid service, however users can try it out for free.  After you type in a word into the search box, results will show up in a web.  Words are color coded by part of speech.  If you click on one of the words in the web, search results for that word will be shown.  Synonyms are connected to the searched word by gray lines and antonyms are connected by red dotted lines.  The search results for the word "find" is shown to the left.

VocabGrabber a free tool on the Visual Thesaurus website.  This tool analyzes a piece of text shows the results as a word cloud.  Users can then sort the text by relevance, alphabetically, number of occurrences, or familiarity.  You can also show words in certain subject areas such as geography, people, math, science, etc. If you click on any of the resuts, you can see related words in a web format.  The image below shows the results for Abraham Lincoln's Gettysburg Address.

Visuwords

Visuwords is a free online graphical dictionary that shows relationships between words in a web.  After you type a word into the search box, and a web will be created to show connected words.  The words are color coded to show the part of speech and type of connection each word has.  If you put the cursor over a word, the definition of that word will appear.  You can also zoom out to see more of the web or zoom in to see it in more detail.  The web below is for the word "smile."