The Department of Homeland Security requests that everyone keeps a 3 day supply of drinking water. As someone who took the Boy Scout motto way too seriously, 3 days is not nearly enough. Water is one of those few pesky things we cannot do without, so the more you can store, the greater your chances of surviving long blackouts or a loss of municipal services.
Our current method of water storage for drinking is 5 gallon containers that we can move about easily. With each container weighing 40 lbs, it's in our best interest to not make them too heavy so most of the family is capable of moving them around. We currently purchase our containers from http://www.containerandpackaging.com/ and have had no complaints in the last 3 years of using them.
Each year, we drag them out of storage, dump them, clean them, refill them, and put them back in storage. The water after a year is still clean, and washing them with bleach helps to inhibit the growth of bacteria. With 10 of the containers, we are only storing a 10-11 day supply for the family, so future projects will involve expansion of our water storage capabilities.