FeedVis is like most word cloud generators, but with some extra goodness:

* You don’t just get one lump o’ words: you can make tagclouds from subsets of your feeds, selecting by blog, time, or both. You can then compare those clouds to ones from other subsets; the animation makes it easy to see differences.
* Any time you’re interested in a word, you can click for more information, including summaries and links to posts that use it.

Most of what FeedVis does is based on two numbers for each word:

* The first is frequency. Frequency says how many times a word is used per 1000 words. If you hover over a word, you’ll see its frequency to the left of the frequency change value.
* The second is frequency change. Often, a word will be more (or less) popular than usual in a certain time period (for instance, « election » in early November). Frequency change measures that difference as a percentage: greener words are unusually popular; redder words are the opposite.