link for Nalgene bottle: http://www.nalgene-outdoor.com/
they make both flesible canteens and hard plastic ones. the wide month makes it easy to clean and you can throw hot water in it without damaging it. ( i remembered once, that a PET bottle filled with hot water shrinked ! ). the mounths are also compatible with MSR water filters. on the side they have markings on how full the bottle is. The flexible canteens are kinda patypus like, but with diffrent mounth's. they also got bigger flexible canteens with handels.