Google Tag Cloud Maker is a Greasemonkey script that aggregates all the words from the titles and snippets of Google search results and creates a box that lists the most frequent words. If you hover over one of the words, you'll see the search results that contain that word in the title or snippet and if you click on the word, it will be added to the current query.
This is a primitive way to refine a query using some information from the search results, but it's also a way to see the big picture, to understand more about your query without visiting each search result.
The idea doesn't work well for all the queries, the popular words are not always placed at the top, and the box also clutters the interface. But it may be useful at times.