A large lightweight towel can be a multitasking take-along, especially if it's made of some soft microfiber that rolls or folds into a diminutive packet.
Sure, it's great for lying on the beach and drying off when the hotel towels are too skimpy or scratchy. But a big towel is also great for cushioning delicate items inside your luggage, makes a good pillow anywhere, and can double as a wrap-around bathrobe twisted and tied behind the neck.
We've found a packable monster of a towel in, well, the Monster Towel. A whopping 10 feet by 10 feet (roomier than a king-size bed) of soft sueded absorbent microfiber, the towel rolls up small and compact. An included carry strap also secures the roll tight at both ends with quick release clip buckles.
The towel has large corner "anchor pockets" you fill with sand to keep it weighed down firmly in place at the beach. You can stash your keys, wallet, or other small items in an inconspicuous sewn-in zippered pocket (not that the towel can't be stolen, but still…).
The Monster Towel comes in six bright colors or basic black, air-dries quickly, and is machine-washable and -dryable.
The Monster Towel is about $90 at monstertowel.com, but can be less expensive at other online retailers.