"Approximately 1 million freely accessible images, videos, documents, and audio files from library special collections, faculty research, and institutional history materials, as well as hundreds of thousands of open access images from the Metropolitan Museum of Art."
An index of the web sites included in the 1999-present annual lists issued by the Mars Best of Free Reference Web Sites Committee of the American Library Association.
"DPLA brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world. It strives to contain the full breadth of human expression, from the written word, to works of art and culture, to records of America’s heritage, to the efforts and data of science."
"Google Scholar enables you to search specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts and technical reports from all broad areas of research. Use Google Scholar to find articles from a wide variety of academic publishers, professional societies, preprint repositories and universities, as well as scholarly articles available across the web."
Articles at this web site explain how ordinary "stuff" works, such as electricity, car engines, the human body, government organizations, tattoos, etc.
Answer questions; do math; instantly get facts, calculators, unit conversions, and real-time quantitative data and statistics; create plots and visualizations; and access vast scientific, technical, chemical, medical, health, business, financial, weather, geographic, dictionary, calendar, reference, and general knowledge—and much more.