My understanding is that the chemical makeup of the plastic is pretty much the same between manufacturers, and what the plastic is, is noted by the number in the recyle symbol on the bottom of the plastic.

Quick survey at home: sports drink bottle and water bottle (those kind that come in 24 packs) are both #1, PETE

A wikipedia page to start with:
http://en.wikipedia.org/wiki/Polyethylene_terephthalate