www.wordsift.com
Wordsift is slightly different than the others in that the word cloud produced is pretty basic. Content area words can be highlighted, and the visual thesaurus allows you to see words in a graphical version. Wordsift has also integrated a few other functions, such as visualization of word thesaurus relationships and Google® searches of images and videos. With just a click on any word in the Tag Cloud, the program displays instances of sentences in which that word is used in the text.
source: www.wordsift.com
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http://tagul.com
Tagul word clouds have some advantages against ordinary text clouds like custom fonts, custom shapes, and support of non-flash devices such as the iPad and iPhone. While the learning curve may be a bit steeper, the results are often worth the time.