Adapted from Literature: An Introduction to Fiction, Poetry, Drama, and Writing, p. 1474
This site is often a good starting point. Wikipedia may be helpful for understanding a particular work of literature and for finding other reference sites. Bear in mind, however, that because literally anyone can edit Wikipedia, it is generally not a reliable source for a reference in your own paper.
Library of Congress’s literary criticism list
These sites have been more or less pre-screened by the Library of Congress.
Internet Public Library
This site is provided by the University of Michigan.
This site is a portal to thousands of libraries around the world.
Voice of the Shuttle
You can find lots of good stuff here.