GreySource provides a detailed classification listing of Web-based resources on the subject of unofficial or "gray literature." Subject classifications include general, multidisciplinary; agriculture, forestry, fisheries, veterinary sciences; environmental pollution, protection, and control; humanities; biological and medical sciences; earth and atmospheric sciences; electronics, electrical engineering, computer science; energy and power; mathematical sciences; mechanical, industrial, civil, and marine engineering; science and technology; and a few others.
Gray literature is defined by this site as "information produced on all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing. … "
