This post was originally published on October 5, 2009, but the Haiti earthquake has given me reason to re-post it and add some additional information.
(The additional information comes first, the original post with a demo video comes last.)
For those looking for a way to help the people in Haiti, Lifesaver Systems is currently offering a buy one donate one special. The USA distributor site is down at the moment, but may be back up shortly. They currently offer 4000 and 6000 liter bottles and 10,000 and 20,000 liter Jerrycans. (Note: Some have been confused about the size of these items: they produce the designated amount, they do not hold that amount.)
The end cost to produce clean water ranges from $0.14 per gallon for the smaller 4000 liter filter unit to only $0.08 per gallon for the larger capacity 20,000 liter (5,283 gallons) Jerrycan.
Here is Lifesaver Systems Frequently Asked Questions page, which is well worth browsing. (Note: there is a separate page for bottles and Jerrycans.)
Michael Pritchard has invented a water filter system that is inexpensive, easily transportable, and apparently very effective. For those living in developed areas, potable water isn't a daily issue for you. However, in most of the undeveloped world, drinkable water is a matter of life and death. A number of organizations have become involved in sponsoring water wells in various parts of the world. This water filter system should not be over looked if you are interested in helping provide potable water for those that don't have easy access to such.