Bartleby.com
http://www.bartleby.com/195/10.html
Bartleby.com is a large site filled with literary references. This part of the site features the complete text of "The Fall of the House of Usher," plus a short biography of Poe and story notes.
The Poe Decoder
http://www.poedecoder.com/essays/usher/
The Poe Decoder elucidates Poe's life and work. This part of the site, by Martha Womack, describes several aspects of Poe's tale of Usher.
The Work of Edgar Allan Poe
http://bau2.uibk.ac.at/sg/poe/
This site is devoted to Poe's life and works and his significance in world literature.