Seeing Air

http://www.reachoutmichigan.org/funexperiments/quick/seeingair.html

http://www.rcn27.dial.pipex.com/cloudsrus/weighair.html

http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/air.html

http://www.eecis.udel.edu/~vijay/BLAST/air_pressure/card_air_pressure.html