Khan Academy offers free practice exercises, instructional videos, and a personalized learning dashboard so that learners can study at their own pace in and outside of the classroom. Khan Academy's content is available for personal, non-commercial purposes.
The UWM Libraries Digital Collections draw from materials in Archives, Special Collections, the Curriculum Collection, Music Collection, and the American Geographical Society Library. Images may be downloaded by individuals or libraries for personal use, research, teaching or any "fair use" as defined by copyright law.
Since its founding in early 2000, the UWDCC has worked collaboratively with UW System faculty, staff, and librarians to create and provide access to digital resources that support the teaching and research needs of the UW community, uniquely document the university and State of Wisconsin, and provide access to rare or fragile items of broad research value. The UWDCC has also partnered with cultural heritage institutions and public libraries throughout Wisconsin to create digital resources. Resources within the collections are free and publicly accessible online.
NYPL holds more than 180,000 public domain items in its digital collections. Easily limit your search to "public domain" images or explore the public domain collections.
The Library of Congress provides access to noncommercial, high-quality content, from digitized photographs, manuscripts, maps, sound recordings, motion pictures, and books, to "born digital" materials, like Web sites. Whenever possible, the Library of Congress provides factual information about copyright holders of the materials but it is up to the user to make decisions about fair use of the materials.
Unsplash provides over 2 million high quality images for free. Photos are openly licensed under the "Unsplash License." All images from Unsplash come from the Unsplash community. Images can be freely used for personal and commercial usages, as long as the images on the site are not used to create a similar or competing platform service