The ceiling fan. Because the tops of the blades cannot be seen, it is easy to forget how much dust can gather up there. Every now and then, lay a sheet or some newspaper down on the floor to collect the dust, step up on a sturdy step stool, then wipe the fan blades with a damp cloth.
Your trash can. Even though it is (hopefully) always lined with a garbage bag, some liquids can seep through the bags, or food particles can get around the outside of the can. This can lead to a buildup of bacteria, in addition to an unpleasant odor. Every now and then, wipe down both the inside and outside of your trash can with an all-purpose cleaner.
The edges of the bottom cabinets. While you may sweep and mop the kitchen regularly, the spot where the cabinets meet the floor is hard to see and reach. Over time, food and dirt can gather here. Whenever you clean the kitchen floors, make sure to get all the way into this crevice.