Google launched Google Trends today (May 10, 2006) as part of Google Press Day. Google Trends allows you to search and compare search data on terms that are entered into a single search field. The layout reminds me of Google Finance but instead of plotting stock information it plots search data with important news tied to the peaks and valleys of the chart. Additionally, the search data can be filtered by date and region.
I think this is a very useful tool especially for the search crazed, search engine marketing professionals and the public relations community. For additional perspectives on Google Trends check out the reviews on TechCrunch and Micro Persuasion.