Once you activate your UNI (University Network ID), you can access resources licensed by the Columbia University Libraries that are not openly accessible online. Among these licensed resources are indexes such as Art & Architecture Source (contains Art Index and others within), Avery Index, EbscoHost Research Databases, Proquest, LEXIS-Uni, encyclopedias such as Grove Dictionary of Art, Encyclopedia Britannica Online, full text indexes and resources such as JSTOR, Project Muse, Archaeopress, Library Stack image collections such as ArtStor, AP Images and thousands of other licensed online resources for which we pay a considerable sum per year. Please understand that you will not be able to access most of these materials if you try to get to them through an open web search (e.g. Google, Yahoo, etc.).
On the other hand, here are several extensive, freely accessible online resources worth knowing about:
A subscription service from the Internet Archive, which allows institutions to build, manage and search their own web archive.
Digital Public Library of America (DPLA). (Online)
The stated aim of the (DPLA) is to bring together the riches of America's libraries, archives, and museums, and make them freely available to the world. This resource offers a single point of access to millions of items including photographs, manuscripts, books, sounds, moving images, and more from libraries, archives, and museums around the United States.
Gallica is a digital library of French and francophone culture maintained by the Bibliothèque nationale de France. Contains numerous electronic texts, images, maps, animation, and sound files of French and other publications in history, literature, science, philosophy, law, economics, and political science.
Internet Archive. (Online)
"The Internet Archive is a 501(c)(3) non-profit that was founded to build an Internet library, with the purpose of offering permanent access for researchers, historians, and scholars to historical collections that exist in digital format; [the Archive] includes texts, audio, moving images, and software as well as archived web pages..."-About IA page.
Includes Wayback Machine for viewing web pages removed from the Internet, archives of images, sound files, music, texts.
And freely accessible online resources for Art History:
Art history resources on the web (Online)
Presents a collection of art history resources, compiled by Chris Witcombe. Includes the following periods/areas: Prehistoric, ancient Near East, Egyptian, Greek, Roman, late antique, early Europe, Islamic, early Medieval, Gothic, Renaissance, Baroque, 18th century, 19th century, 20th century, contemporary, prints & photographs, Chinese, Japanese, Indian, Southeast Asian, African, the Americas, Pacific cultures, research resources, miscellaneous, museums & galleries.
Art and art historical portal realized thanks to financial support from the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG), as a common project of the Library of the Zentralinstitut für Kunstgeschichte in Munich and Heidelberg University Library in co-operation with the Institute for Art History of the LMU Munich (chair Professor Dr. Hubertus Kohle) together with the historical network historicum.net and further partners. arthistoricum.net focuses the core competencies of the co-operating institutions into a fundamental platform for research and teaching. It includes the following sections: Electronic Journals Library, ARTicles online-Art historical articles from e-journals, artlibraries.net (listed below), Art historical institutes, etc.
CODART (Online: http://www.codart.nl/)
An International Council for curators of Dutch and Flemish Art. This site is self-described as the best guide to Dutch and Flemish art in museums worldwide.