Google Dashboard is intended as a transparent way for you to see what Google services you're using and what sort of information is being stored on Google servers. Since Google's AdSense advertising uses information gathered about you to serve targeted ads, your recent search history or other activity may give you clues about why you may be seeing particular ads.
Not all Google products are shown in Google Dashboard, but Google plans on expanding the service. Google also hopes other companies create similar dashboards for their products.
Google Dashboard is on the Web at www.google.com/dashboard