A hat tip to Rebecca Writes for turning me on to an outstanding Bible study site. The Bible Centre has the usual collection of public domain books, along with some surprisingly newer ones. Look at this:
The Commentaries section includes works on 1 Thessalonians and 2 Thessalonians by F. F. Bruce. New Testament Studies include the Westcott-Hort Greek NT text from 1881 with NA26/27 variants, Bruce Metzger's
Textual Commentary on the Greek New Testament, F. F. Bruce's
The New Testament Documents: Are They Reliable? and Gerhard Kittel's multi-volume
Theological Dictionary of the New Testament.
The section on English Bible Versions includes Charles Ryrie's
Inerrancy and Bruce's "The Two Testaments." The Reference Library has e-versions of two textbooks I studied in seminary: Dillard and Longman's
Introduction to the Old Testament and Carson, Moo and Morris's
Introduction to the New Testament. There's also a fine Bible map collection and an interesting book, new to me,
Dictionary of Bible Types by Walter Wilson. The Theological Library has John Piper and Wayne Grudem's
Recovering Biblical Manhood and Womanhood along with works of both Calvin and Arminius.
There's some exceptionally good material at The Bible Centre. Along with this post, I'm adding links to the map collection and center main site.
Update: On closer examination, it looks like The Bible Centre may be violating copyright law by posting some of the newer works. I've removed the links to all pages and will leave them off till I'm convinced they're not copyright violations.