Several sources have told me that to cut down on monthly costs you need to reign in your food budget...or at least pay attention to what you spend at the grocery store. John and I use a computerized envelope system and it has worked for us. Here is the specific program we've used for 9 years. Beyond that, I plan meals from sale flyers.
This Proverbs 31 woman posts links (one is an ABC video) about cooking from the 99 cent store. Interesting.
A cookbook that I've enjoyed in the past is Miserly Meals: Tasty recipes for under 75 cents per serving. (I don't use cookbooks much these days - I prefer using allrecipes.com)