Towels are that rare item that every hotel provides, and that's very good news for an inventive traveler, as they can be used in so many different ways. For one, you can use a towel to block any outside noise, light or cold in a hotel room by simply rolling it up and placing under the door.
A towel can also help you if the air in your hotel room is too dry. Simply wet the towel, hang it on a chair and move the chair close to the air vent, and voila! You have a DIY air humidifier.