For plastics, anything that is made for drinking water purposes is good. Some people successfully use gasoline/kerosene containers, though I'm not comfortable with that.
For water changes, I've been using a 7 gallon water jug (blue) that I bought at Wal-Mart from the camping section. For my ATO container, I'm using a 5 gallon square-shaped plastic water container that I bought from LFS; it sits inside the stand and its fed via a peristalic pump thats controlled by a float switch in the main tank.