Earth science NOVA Episodes:
Tornadoes:
Hurricane Katrina- the Storm that drowned a City: http://www.pbs.org/wgbh/nova/earth/storm-that-drowned-city.html
Biology
Cracking the code of life; http://www.pbs.org/wgbh/nova/body/cracking-the-code-of-life.html
What Darwin Never Knew: http://www.pbs.org/wgbh/nova/evolution/darwin-never-knew.html
Where did We come from?: http://www.pbs.org/wgbh/nova/evolution/where-did-we-come-from.html