Treatment Systems for Household Water Supplies - Activated Carbon Filtration
1992 article from the North Dakota State University Extension Service explaining in detail what activated charcoal systems can and cannot do.
http://www.ext.nodak.edu/extpubs/h2oqual/watsys/ae1029w.htm

Home Water Treatment Using Activated Carbon
Discussion and guidelines from a 1997 article from the Michigan State University Extension.
http://www.msue.msu.edu/msue/imp/modwq/wq239201.html

HowStuffWorks: Reverse Osmosis
How does reverse osmosis work to purify or filter the water?
http://www.howstuffworks.com/question29.htm