How a hydroelectric generator works:
http://science.howstuffworks.com/environmental/energy/hydropower-plant1.htm
http://ga.water.usgs.gov/edu/hyhowworks.html
How a coal-burning power station works:
http://www.energyfutures.qld.gov.au/how_a_coal_fired_power_station_works.cfm
http://www.hk-phy.org/energy/power/elect_phy/flash/powerplant_icon1.swf
How a nuclear power station works:
http://a-agung.staff.ugm.ac.id/wp-content/nuctour1.swf
http://science.howstuffworks.com/nuclear-power3.htm
How a solar cell works:
http://www.odec.ca/projects/2006/wong6j2/solarAnimation.html
http://simeonintl.com/files/A_flash_demo_how_solar_panel_works.swf