The Dissertation Reviews' listing of archives is a wonderful resource for research students, written by students based on their real experience in using archives. The section 'Fresh from the Archives' is especially helpful if you are preparing your trip.
Asian Art Archives (focused on East, South and Southeast Asia)
This is one of the most useful resources I use regularly to verify art history dates/period/era, and the World Maps is also a possible citation source but the maps cannot be downloaded. Note that the database is very much oriented to (MoMA) Metropolitan Museum of Art's collections as the Timeline is compiled by their curatorial, conservation and education staff.