The Canadian Museum of History has a variety of exhibitions (current, online, traveling) that you can browse through to find those on ancient art (e.g. Mysteries of Egypt).
The Boston Museum of Fine Arts has a large collection for art of the ancient world. You can browse subsets of this collection towards the bottom of the page, which lead to brief online tours of the subject.
Associated with the University of Vermont, the Fleming Museum of Art includes has a collection dedicated to ancient art and artifacts. Unfortunately, the collection cannot be searched separately from their general collection.
Browse the Curatorial Departments at the Met to find the most suitable category of ancient art (e.g. Greek and Roman Art) to learn more about the collection as well as see items from that collection online.