http://www.paradiselost.org/
A clear and informative study guide about Paradise Lost, including an overview of the  poem, information about  Milton’s life, book summaries, character descriptions, essays, illustrations and much more.

http://www.gutenberg.org/ebooks/20
The Project Gutenberg edition of Paradise Lost. You can download the text in a number of formats, or read it online.

https://facultystaff.richmond.edu/~creamer/milton/audio.html
A website “devoted to the life, literature and times of John Milton”. On this page, you can find audio files of Paradise Lost and other works by the author.

http://www.dartmouth.edu/~milton/reading_room/contents/index.shtml
The Milton Reading Room is a superb website created by Professor Thomas Luxon and his students at Dartmouth College. The site contains all of Milton’s poetry in English, Italian, Latin, and Greek, and a selection of his prose. All of the works presented are fully annotated.

http://www.universalteacher.org.uk/poetry/paradiselost.htm
A Paradise Lost study guide for undergraduates and general readers who are interested in the study of poetry. The site includes useful information about the content and structure of the piece.

http://novelinks.org/pmwiki.php?n=Novels.ParadiseLost
A website aimed at literature teachers, including a list of pdf worksheets about Paradise Lost and themes of such as authority, obedience and rebellion. Especially adequate for young learners of the text.

http://www.wwnorton.com/college/english/nael/17century/topic_2/welcome.htm
The online Norton Anthology of English Literature contains extensive contextual information about the early seventeenth century with a page entitled Paradise Lost in Context, with references to Milton’s main influences in writing the work.

http://www.cummingsstudyguides.net/ParadiseLost.html#Milton  
A useful study guide about Paradise Lost, written by Michael J. Cummings, covering topics such as the text’s sources, settings, characters, style and verse format, epic conventions and imagery, as well as numerous study questions and essay topics.

http://theses.gla.ac.uk/1358/01/1999robertsonphd.pdf
Lynne M. Robertson’s 1999 thesis, dealing with Renaissance tragedy and Paradise Lost. The work is structured around three main sections, each of which identifies a dominant theme in the drama and poetry of the 1580-1670 period.