And even more important, storing a list of all the things that you buy regularly - really handy for anyone in charge of keeping things at hand for something like a school photography program.
B&H's wishlist function (as an example) gives you the ability to have separate lists for separate categories - e.g. film in one, darkroom chemistry in another, printing paper in a third - as well as giving you access to a single page that lists availability and pricing information of everything you buy regularly. B&H's system also allows you to easily add something on your wishlist to your shopping cart.
It also serves well as a pure wish list - a list of all the things you would love to have, if and when the budget permits.