I'm not talking about anything big -- just the little things that add up, things that other people might not consider doing. Here's something I just did:
Last night I sautéd a yellow squash, a zucchini, and an onion as a side dish. We had perhaps 2/3 a cup of vegetables leftover. No one would've eaten those as leftovers. Knowing I was going to make chili tonight, I saved them, chopped them up finely, and hid them in the chili. It bulked up the chili, perhaps adding one more serving, and it added some extra veggie-power to the chili. No one else will even know that last night's vegetables are making a second appearance.
Also, earlier today I took a ziplock of homemade soup to work for lunch. I made it a month or so ago, and no one else in the family liked it . . . so instead of watching it slowly go bad in the refrigerator, I froze it into individual portions for my own lunches. Added benefit: I love having homemade ready-to-go lunches. Negative: If I leave them in the refrigerator at work, the night janitors steal them.