String, so simple and small. I bring string with me on medium length trips – over a week to a month or two in length. The length of a trip where you can’t pack clothes for ever day, but not so long that it’s easier to just buy an actual travel clothes line.
It goes with my laundry soap to dry my clothes. While some hotels have clothes line in bathrooms, not all do. And do you really want to hang your clothes on the furniture of a hotel room? All you need with string is two points to tie the string to and you have a clothes line, simple! And since it’s cheap you can just leave it behind. I try to bring enough string to last a few dryings.
One nice spot to hang clothes in the winter is over the heater. You’ll want it a few feet above so it doesn’t start a fire, but the warm air will improve the drying time.