SparkNotes has an excellent summary of Homer's epic poem, "The Iliad." It contains a large plot overview alongside more in-depth summaries of the individual books of the poem as well as themes, questions, an analysis of each major character and other study guides.
Readers can also find a quality summary of the plot and each individual book from CliffsNotes. This website also contains character studies, a biography of the author, maps, example essay questions and other useful study guides. The summary of "The Iliad" available on eNotes.com, which has an overall plot summary but no other study material, provides another option.