Multi-purpose hotel shower caps: Beyond using these to keep your hair dry, how about wrapping one around each shoe to keep the rest of the items in your luggage protected? Or slip one over your camera lens to keep light mist off the lens when you’re shooting photos.  I also wrap a shower cap around a can of hair mousse or hair spray, as these are the two items that most leak in my luggage.  They’re also good for wrapping around anything not fully dry, such as a damp bathing suit.