The Commentary to the Douay-Rheims translation of the Bible by Father George L. Haydock, generally found at a price of $100 or more apparently has been recently placed on the Internet with the following cautionary statement:
WEBSITE STATUS: Raw transcription completed and posted online, December 2007. First proofreading of all chapters is now in progress. Please report any suspected transcription errors via email to: CatholicBook@aol.com. Thank you.
I just glanced at the notes on John, Chapter 6, The Bread of Life discourse; There are 36 extremely detailed notes on that chapter alone.
The Haydock Bible Commentaries are found at http://haydock1859.tripod.com/