Milk going bad?  A teaspoon of pure vanilla extract added to a gallon of milk near expiration can kill off the bacteria in the milk without altering its taste to a noticeable extent.

Run out of fabric softener?  Distilled white vinegar works as a cheaper alternative to typical fabric softeners.  You might miss the ERA fresh scents, but you’ll probably appreciate the extra cash as the vinegar smell washes away as it softens the fabric.