Space shuttle crewmembers can choose to wear pants or shorts depending on what they're doing aboard the shuttle and the temperature inside the spacecraft. They also have the option of wearing long- or short-sleeve polo shirts or rugby shirts, as well as sweaters and pullovers.
Like space station crews, shuttle astronauts wear shorts and T-shirts when they exercise. The pants they wear are covered with plenty of pockets and velcro. The pockets and velcro help them keep everything they're working with near them. Without gravity, anything a person lets go of will float away - to be found later on the filtering screen of the shuttle's air circulation system. This screen is the shuttle's version of the Lost and Found section. Station crewmembers also report finding their lost items on the screens of the space station's air circulation system.