For non-drinking purposes I think I'd use rain barrels or fill a 33 gallon PVC garbage can and with water and add an ounce or so of bleach. Sound reasonable?
I found an online source of food grade polyethylene trash can liners a while back. If anyone is interested I can probably locate the URL again and post it here. The idea is to be able to use garbage cans to store drinking water by lining them with those bags. Of course there are 55 gal water drums, but they're ridiculously expensive compared with garbage cans.
I looked at the Aqua-tainers at REI and they seemed reasonable though there was room for improvement. The main problem I saw was with the air vent, which was just a plug that could fall out if the container got banged around (I was looking for a car container). For home use they're probably fine.
These things intrigue me but I haven't tried one:
http://aquaflex.net -- flexible flat tanks, up to hundreds of gallons in size, and relatively cheap.
Finally, if it's something like a hurricane where you have advance warning, a standard preparation step is to fill your bath tub(s). Make sure ahead of time that the drain plugs don't leak.