Rijksmuseum Collection
rijksmuseum.nl/en/collection
The Rijksmuseum's online collection of Dutch art and history, including works by Rembrandt and Vermeer, with high-resolution images of public-domain pieces.
Why it is useful
Lets you zoom in on famous paintings in extraordinary detail and download public-domain images. It also holds prints, drawings, photographs and objects, so you can browse well beyond the famous names.