Definitely check out the Platypus bottles. I have 1L and 2L bottles, and a hydration hose plus the spout caps, and they're great. They are durable, they weigh next to nothing, and they're relatively inexpensive. When they're not full of water you can fold or roll them up and pack them away.

I've used mine for all manner of hiking, backpacking, snow camping, and backcountry adventures, and never had a problem.