I'm sure everyone already knows that you can save money by buying larger portions but here's an example - raviolis, which is favorite lunch of my daughter and her friend when they come home from kindergarten.
I was buying the canned type (I know, not so healthy) but the today I cooked up a half bag (bag is 16 oz) of Trader Joe's dried ravioli's and half a bag of their tortellinis (the girls couldn't make up their mind so we made both) and added a jar of Trader Joe's tomato and basil marinara (cause it was cheapest:) I fed them, sampled some myself and put the rest away.
It should last for a couple more lunches. Not much more prep time, tastes just as good, if not better and saves me money. Good buy all around.