When I was doing extract recipes, I used chilled gallons of bottled water that had not been opened. Never had a problem.

Glass is the best, but I use a few plastic bottles with each batch for one reason. I like to take some beer to the lake or the beach- and no glass bottles are allowed. I keep them in a dark place and don't count on them for long term storage.

I have used almost all of the ones mentioned in this thread as well as Rebel Brewing in Tennessee. There is no one right answer- shipping costs vary depending on what you are buying. My 2 favorites are Austin Home brew and Rebel Brewing.