"צביעה באוכלים" (coloring in foods) - the stringent view of some poskim
דבר דבר (Dabair Davar): Calculations for a סעודת מצוה Seudas Mitzvah;
Salting a Salad by Itself: Is One Allowed to Salt a Vegetable in One's Hand When Eating It?;
interesting cases that come up with items that are not made to stay in their place all the time.