Wordle lets you generate word clouds from text that you provide. You can tweak your clouds with different fonts, layouts, and colour schemes.
After a big drop down the list last year, Wordle has regained a few places this year.
Comments from some of those that selected Wordle as one of their Top Tools
“a creative way for students to brainstorm and synthesize” Diane Lowery 2014
“this is just so much fun; great to create artwork for a classroom; I create a poster for outside my class door the first day of class” Sarah Davis
“Word clouds. Nice for topic starters.” Leia Fee
“A great web app where you can generate world clouds from the text that you provide. Paste in text, rss url or del.ico.us username.” Scott Hewitt
“Input some text, then get a highly visual “word cloud” illustrating which words are most frequently used. Throws out some very interesting results when used with famous speeches, poems, constitutional documents.” Rusel Tarr