The National Media Museum of the United Kingdom includes images from their extensive media archives. The images are grouped thematically in order to demonstrate the diversity in their collections. They have publicized them through Flickr and The Commons, which encourages many public collections to be digitized and shared.
The New York Public Library has digitized much of their collection, with the idea of it being a living and growing database, with regular new additions. The collection includes photographs, manuscripts, maps, videos, and more.
Great Images in NASA contains images from the NASA archives, including categories of Space Exploration (obviously), Historical Research, Astronomy, People, etc. These NASA images catalogue the various missions, including the Apollo Program, Skylab, Gemini Program, various spacecraft, and so much more.
The J. Paul Getty Museum, owned by the J. Paul Getty Trust, maintains their website in order to further artistic and scholarly information to aid the public. The Museum collections include digitized versions of their antiquities, drawings, manuscripts, paintings, photographs, and sculpture and decorative arts. The main focus of the J. Paul Getty Museum is to nurture the curiosity and enjoyment of the visual arts. Their collections are extensively curated, and they are easily searchable.