Antigone is the story of the title character, a fiery heroine who seeks to bury her brother after his failed attempt to rebel against the ruler of Thebes, the powerful Creon. Creon has decreed that her brother's body is to be shamed publically. Antigone's rebellion against Creon sets off a chain reaction of suicide, defiance, and emotional devastation that claims her life and leaves the ruler a broken man.
Boasting the largest collection of book summaries, BookRags is the best option for titles you can't find elsewhere. They offer all of the basics (quotes, chapter summary, characters, historical context, literary criticism) but also walk through a few major topics that recur throughout the book, which can be particularly useful for essay writing.
The most popular website for book notes. SparkNotes was created by students for students, and their summaries are accessible and extremely well-written. Besides the usual plot overview, chapter summaries, and character analysis, SparkNotes differentiates itself with a section discussing themes, motifs, and symbols.
Their book summaries aren't as good as other providers, but PinkMonkey often has interesting insights that aren't mentioned elsewhere on the Internet. For example, they go over literary elements (like setting, conflict, and mood), compare and contrast, and symbolism/motifs. It's a good site if you want to find a unique fact or angle that other students don't know about.