I was all ready to jump on the stainless-steel bottle bandwagon, until I kept finding over and over that they were lined with plastic anyway. I bought a cute little unlined Surly one made in China that said "stainless steel"... it made things smell funny and magnets didn't stick to it. (so, obviously not steel)

Into the recycling bin and off to the smelters. I'm guessing it was actually aluminum or pot metal.

SOMA Crystal bottles are my favorite. They are polypropylene, so not even in the same plastic family as the BPA plastics or the smelly flexible plastics. http://somafab.com/bottle.html They don't grow funny cooties, either. They've lasted longer than any of my other bottles and survived neglect and abuse.