Complete Bible Commentries.. Open Access Digital Theological Library
The commentaries are, for the most part, from pre-20th century; however, that does not diminish many of the contributions they have made to biblical scholarship. As with most things, many of these commentaries are "out-of-date" in many respects but that does not dismiss many of the important information provided.
This link will take you to the OADTL catalog. Once there, click on the View eBook button to gain access to the materials.