I was over the moon upon discovering Coudal Partners Museum of Online Museums and their exhaustive collection of collections, ranging from the Bodleian Libraries and Amsterdam's Rijksmuseum to:
Galleries, Exhibitions and Shows
Trust me, clicking on that first link was not as satisfying as one might suppose.
However hope springs eternal and, as they say on their MoOM page:
Thursday EditionGet lost in our MoOM, The Museum of Online Museums.