For the Force and Motion crowd
Open Google.com, and enter the words "Google Gravity" in the search bar. Then click on "I'm feeling lucky" under the search bar. Watch what happens to your screen. Is this really gravity at work?
If you can't make the above happen, click on http://mrdoob.com/projects/chromeexperiments/google_gravity/ instead, and the click on "I'm feeling lucky" as above.
Click on another open tab in your browser, and then come back to the Google page. Watch what happens. Could there be wind in your computer?