Food shopping is an area that the seriously frugal can work on quite easily.
Many places advise menu planning, and for many that works well. For my family we got bored with the same recipes over and over, so we looked at how to plan a menu for the week.
Nik and I came up with themed meal days. It sounds a bit cheesy and school dinnerish, but it does make planning a week's dinners much easier. This is the week of themes that we are currently using:
Monday - Meatless Monday
Tuesday - Pinterest Tuesday
Wednesday - World Food Wednesday
Thursday - Throwback Thursday
Friday - Fishy Friday
Saturday - Speciality Saturday
Sunday - Sunday Roast
We only plan for the main meal of the day and often cook enough so that there are leftovers ready for lunches.
Using themed days means that we explore different food from different places and time periods. It takes some of the familiarity out of eating and allows us to make a weekly shopping list that we can stick to rather than going to the supermarket and picking up random things because we have no idea what to cook. The first few weeks can be based on ingredients already in stock. If you're a bulk buyer (we are - we get great discounts!) You can base much of the menu around your bulk purchases.
Try theming your menu to spice up your eating habits and slim down your spending.