I stumbled upon this Book Search site (created by Microsoft Research in the UK) that has some 50,000 digitized books -- especially strong in Religion & Philosophy, Christianity, Bible, Doctrinal Theology, and Practical Theology categories. It looks like all older books (public domain, out of copyright). You can browse, search, download, read and annotate. From what I can tell many of these books are not available in Google Books with full digitized content as they are here:
http://www.booksearch.org.uk/
This looks to be a research project that was only very recently presented at a conference (this past November). Just our luck that the collection of books they decided to digitize to test out the concept is mostly theology books! So play with it while it's free. I'm sure they'll be looking to monetize this at some point in the future.
[Note: I'm going to start using "Off Topic:" spelled out instead of OT: as there are probably a lot of forum newbies around here who don't know the standard abbreviation OT, and it means something else in the Logos context.]
