The couch is sort of like your pillows or mattress -- you spend so much time on it, and have probably never cleaned it. A vacuum should be used regularly to remove dust, dirt, hair, and dander, and an upholstery cleaner like Resolve can help with spot-treating stains from spilled food or drink, or for cleaning off general grime.
The dish rack and dishwasher
For slightly different reasons, the place where your dishes go after you've used them should get a bit more of your cleaning attention. Drying racks will absolutely develop mold and mildew because of their constant exposure to water. That means you're ostensibly clean plates, bowls, cutlery, and drinkware are going back in the cabinets with bacteria on them that you probably don't want in your mouth.