The Harry Houdini Collection, with 779 items made public and searchable. Magic, both stage conjuring and occult. Also stagecraft, selected folklore (e.g. Cornwall) and myth, and more.

More recently on Archive.org, the Illustrated London News 1842-2003 is still being loaded, albeit from microfilm so the pictures are not great. But they’re not too bad, and it is thus made easily and quickly searchable. A possible source of portraits of 1920s writers, and various historical snippets about the British Isles. So far as I recall, the run is paywalled in the UK.