I was reading my copy of the Icelandic Sagas, and in the Saga of the People of Vatnsdal it mentions that Ingimundur and his crew fought a different Viking crew (Saemun's) with "arrows and stones".
How common was the use of thrown stones among Vikings? How about their use among European armies? Arabic?
Konungs skugg sjá mentions that stones are good weapons to use when fighting aboard ships. Beyond the fact that they're literally free, they're readily available on ships, as they're used for ballast.
Vatnsdæla saga, Sverris saga, and just about every other saga that involves a ship-board battle involves rocks being hurled. If I recall correctly, they're thrown at Egill and his men in Kurland in Egils saga, too, when they're on foot.