Excavation Reports
Check the publications of the institutes listed below. The American School of Classical Studies at Athens, for example, provides open-access pdfs of many of its volumes on Corinth, the Athenian Agora, and Hesperia Supplements. Although it was published in 1976, the Princeton Encyclopedia of Classical Sites, is a handy source for site bibliographies. Grove Art Online has entries for many major sites with references to past and recent publications. Search BULS for publications. If unavailable, request them via Interlibrary Loan.
Egypt
Greece
Iraq & Iran
Italy
The Levant
Turkey