The Princeton Shahnama Project is an "archive of book paintings--commonly known as Persian Miniatures--that were created to illustrate scenes from the Persian national epic, the Shahnama (the Book of Kings). The Shahnama is a poem of some 50,000 couplets that was composed by Abu'l Qasim Firdausi over a period of several decades in the late tenth and early eleventh centuries. The core of this archive is a fund of 277 illustrations from five illustrated manuscripts of the Shahnama that are housed in Princeton University's Firestone Library." The site also has the complete Shahnama in the Warner & Warner translation but here's another translation by Helen Zimmern [more inside]
The Islamic art collection at the Los Angeles County Museum of Art has beautiful objects to delight every fancy, whether you seek manuscript illustration (more), calligraphy (more), glassware (more), archetectural elements (more) and much, yes, more! If you want some knowledge to go with the beauty then you are in luck because on the site there is an overview of Islamic art history from inception to the now.
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).