The Folger Shakespeare Library has announced that its editions of 12 of Shakespeare's best-known plays are being made available free of charge digitally (together with their full source-code), and that the rest of the plays will follow next year:
Users can read the plays online, download PDFs for offline reading, search for keywords within a single play or the whole corpus, and navigate by act, scene, line, or the new Folger throughline numbers. Every word, space, and piece of punctuation has its own place online
Plays are also displayed with the same page numbers as in the Folger Shakespeare Library print editions to allow the two to be easily used together in classrooms.
The Folger Library has lots of other helpful resources for teachers and pupils too.