The internet provides open access to a tremendous amount of information, including peer reviewed, scholarly material. However, be mindful of your sources. Consider the following:
Authority - Who is the author? What is their point of view?
Purpose - Why was the source created?
Publication & Format - Where was it published?
Relevance - How is it relevant to your research?
Date of Publication - When was it written?
Documentation - Did they cite their sources?
Google Scholar - Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines.
Art21 - Art21 is a nonprofit organization dedicated to inspiring a more creative world through the works and words of contemporary artists.
Heilbrunn Timeline of Art History - The Metropolitan Museum of Art's Timeline of Art History. See illustration below.
RIBA Architecture - From the Royal Institute of British Architects, this site explores architecture through articles, exhibitions, and images.
Dutch Paintings of the 17th Century - This site features an exploration of the Dutch Golden Age through the National Gallery of Art's paintings.
Art & Humanities: Art History - A complete set of essays in art history from Kahn Academy covering traditional, non-western, special, and global topics.