The MoOM is a massive link-list to online galleries on just about everything. Yes, there are all kinds of “worthy” collections like The Bauhaus Archive, Duke’s Rare Books and Manuscript Library, and The Slide Rule Resource Center but I defy anyone not to spend at least as much time diving into Big Things of Canada, The Vintage Typewriter Museum Gallery, and The Condiment Packet Gallery. (OK, maybe not so much with the Condiment gallery.)
Whether you are looking for a comprehensive collection of Vermeers or airline spoons, the MoOM portal is nicely laid out with thoughtful captions...of course, once you get into the individual sites, you’re on your own.
(FYI: Before you go looking, The Gallery of Parisian Windshield Flyers is no more interesting than it sounds.)