Many of you may already know about this, but I just recently discovered Answers.com by clicking the "definition" link in the upper right of Google's results page. This is a beautifully simple site that provides what they call "snapshots" of information on over a million words, topics, etc. One one page, they deliver results from dictionaries, encyclopedias, glossaries, atlases and many other types of reference sources. In many cases, they provides just the info you need without having to click through dozens of search engine pages. You can also download free browser and desktop plug-ins allowing for what they call "1-Click Answers" where pressing Alt+click on any word will initiate an Answers.com query.
My company is currently going through some internal marketing activities and I have found this site very helpful for quickly and broadly drilling down into into words and phrases as I think through potential marketing language. They are definitely on to something.