Al-Jazari is the best-known Islamic inventor of the Middle Ages, famous for his waterclocks and automata. The wonderful History of Science and Technology in Islam has articles on him as well as other subjects. A medieval manuscript of Al-Jazari's masterwork, a book generally known in English as either Book of Knowledge of Mechanical Devices, can be perused in its entirety in flash form. It includes 174 illustrations. If you want to see working copies of his most famous automaton, the Elephant Clock, you can go either to the Ibn Battuta Mall in Dubai (Flickr pictures), the Musée d'Horlogerie du Locle in Switzerland (Cabinet of Wonders post about visiting the museum) or Institute for the History of Arab-Islamic Science in Frankfurt (article about the institute from a feature in Saudi Aramco World magazine called Rediscovering Arabic Science).