I used to constantly forget to take my reusable grocery bags with me when I went shopping, so I decided to keep them in the trunk of my car. Now, I constantly forget to take them into the store. But I (almost) always remember my purse. These keychain tote bags fold up to just 4-1/4 inches by 2-1/4 inches — smaller than a back of cards — so even two or three of them take up barely any room inside my purse. But they open into a roomy 15-inch by 15-1/4 inch by 3-1/2 inch carry-all — plenty big enough to haul some serious groceries (or souveniers, if you like to travel).

$9.85 (two or more, $7.85 each) at Magellan’s.