Harry Potter Cliff's Notes
I went out yesterday and bought the top-selling Harry Potter and the Order of the Phoenix (at the supermarket, of all places) and immediately ran into the problem that the last massive tome had completely escaped my mind these last two years. Beyond the general outline and some of the main characters, a complete blank. Google came to the rescue and provided me with this reading guide to Book 4. There, now that's better.
Revision added 4 Sep 2003: I noticed so many hits on this page in my referers log that I thought I had better direct people to the information on Book 5 chapter summaries too. But remember, if you're using these for a summer book report, be sure to cite your sources!