Shakespeare, the complete works. Maintained by the Classic Literature Library, UK. Excellent resources. The latter has on-line editions of the King James Bible, Sherlock Holmes,Charles Dickens and Charles Darwin, Bram Stoker and several others.
A Guide to Shakespeare's Plays .Provides a very brief synopsis for each of Shakespeare's works (on or below par with Cliff Notes) and a link to the full e-text at the University of Virginia Libraries.
Mr. William Shakespeare "A complete annotated guide to the scholarly Shakespeare resources available on the Internet." A very fine resource.
The Victorian & Edwardian Theatre Collection's Theatre History Resources at the Templeman Library, University of Kent at Canterbury, and the Theatre History Collection. Excellent links to 17th, 18th and 19th century resources, with a special section on the Savoy Operas.