There are many good electronic resources available online. However, just as with printed texts all such resources must be carefully evaluated by anyone reading them.
Old Testament
Keil and Delitzsch, Biblical Commentary on the Old Testament, 1
Keil and Delitzsch, Biblical Commentary on the Old Testament, 2
Keil and Delitzsch, Biblical Commentary on the Old Testament, 3
Keil and Delitzsch, Biblical Commentary on the Old Testament, 4
New Testament
Peter Achimugu College of Theology, Ankpa 