There are vast collections of primary sources available on the web. Keep in mind, however, that much online content has not been filtered and evaluated like most books, magazines and journal articles. Thus the burden is on you to evaluate your sources for credibility.
Pay particular attention to Currency, Relevance, Authority, Accuracy, and Purpose (yes, that spells CRAAP!) Using NoodleTools to cite your web sources also helps take you through an evaluative processs as you look for the availability of each piece of bibliographic information.