You can get 16 oz. miller lite in brown PET bottles. My Local Home Brew Store (LHBS) wants $17.50 for a case of brown PET empties + $3.50 for the caps which he says are reuseable up to 3 or 4 times. I got a case of the Miller Lite from the package store for $25.
So I figure if the case of bottles and caps would cost me $21 I'm getting a case of Lite for $4. I can afford to give the stuff away at that price.
Any time I go to a party I take at least a 6 pack of Lite and tell people to save the bottles and caps.
Also there's a device call a carbonator ($12) that screws onto standard plastic bottle cap treads such as 1, 2, and 3 liter and any of the smaller sizes 8-20 oz. It's expensive for what you get IMHO but you can force carbonate and repressurize after you've opened a bottle if you have a bottle of CO2.
I bought 1 but I should have put the money toward buying a cornie keg.
But it kind of cool to take places where you can't take glass or Aluminum cans or cornie kegs.