Three Greek museums–the Acropolis Museum, the Benaki, and the Museum of Cycladic Art–have made available portions of their collections via the Google Art Project. This has been widely reported in the press, and academic circles, but it can’t hurt to mention it one more time. There are ca. 150 museums from ca. 40 countries involved in the project now. The interface is easy to use, and you can view and study the objects more closely than you would otherwise be able to at the actual museum (the high-res details are really fantastic). You can also build personal galleries, search the collections by artist or location, and take virtual tours of select museums. The Benaki collection seems fairly large–some of the old photos and drawings of Greece are esp. enjoyable (including one of Korinth in 1897).
Here’s a link to the collections involved: