While I love saving money, I really dragged my feet on this one. I don't know why, but I just did not want to do it. Now that I have been menu planning for over a year I can promise you it is worth the effort. If you are really busy then a menu is a must! You will not only save money, but time as well. I plan my menus for one month at a time (weekly can work too). When I sit down with the calendar, the first thing I do is mark all the games, meetings, etc. so I know what nights I need a quick meal. A planned, quick meal means no fast food, which saves us a bunch of money.
The real key to saving money with menu planning is to do it backwards. To save money, you DO NOT plan a menu and then go shopping for the needed ingredients. You shop, taking advantage of the deals and sales, then plan your menu around what you have in your pantry and freezer. That way you are getting the best deals and using what you have. Always keep an eye out for sales on the items you use most. When you see a good deal...STOCK UP! When you use what you have and only use items bought at low sale prices you save even more!
I have menus for breakfast and lunches too. Those aren't as creative as the dinner menus, but I didn't just want to have cereal every morning either. So I made a two week rotating breakfast and lunch menu. I don't even have to think about what to make for breakfast or lunch anymore! I love it! I always know what to stock up on (saves money!) because we have the same 10 things! Since half of our family can't read yet I put together a clipart menu for the rotating breakfasts and lunches; the kids know what to expect and really hold me to the menu. Now not only do I save money, I don't have to wonder what to make, AND I don't have to answer the dreaded question: "Mom, what are we having...?"
Here are a few additional links to help with menu planning if you are interested:
Family Grocery Budget
Money Saving Mom
The Simple Dollar
[I wrote this (minus the links) for my twins club newsletter but thought I would share it here as well.]