1 liter plastic pop bottles (not water bottles.) You can buy cheap store-brand club soda or tonic water for less than $1 per bottle, and they work great for beer. Store them in a dark place (like in a box) so the light can't skunk your beer.
You can even use 2 liter bottles. I never have because that's usually more beer than I want to consume in one sitting.
That's what I was going to say. Soda bottles are perfect- designed to hold pressure, and free/cheap if you're a soda drinker. We have tons of soda bottles going into recycling at work, so you could pay 10 cents a bottle and your work would make out and no one would have to haul them to recycle them. You do need the caps, though!
Mason jars are designed to hold a vacuum, and not pressure, so probably the seals will blow long before the glass but not always.
