Remember that volcano experiment back in grade school? You can have fun re-creating that on a regular basis in your bathroom drains—both the sink and shower. Just pour a cup of baking soda down the drain followed by one cup of vinegar. Put a damp washcloth or cover over the drain and let the mixture fizz away, blasting away built-up gunk to keep the water moving. Wait about 15 minutes, then pour a kettle's worth of boiling hot water down the drain to flush.