I second the above recommendations of Calvin's set; I can think of no better place to start (and few better places to end); Keil and Delitzsch are also frequently priceless as a set. Henry on the OT is unbeatable for homilectical and devotional commentary: there might not appear to be much detailed exegesis or critical work, but this commends his mastery of these things. In addition, though they might be more technical than you're looking for: Ainsworth is gold; and Poole's Synopsis (not his Annotations), as I have begun to discover, is a work in a class of its own. The Matthew Poole Project is currently translating this into English and publishing it, and I would encourage students of scripture to pass on eating for a week if such funds will help you procure these books.
The following is far from a comprehensive list, but includes those OT commentaries which immediately entered my mind as being some of my "favorites," which are yet available, accessible to laypersons and in English. Young and Waltke may be a bit technical, but they are just that good that I couldn't restrain myself. If I have time later, and this thread hasn't advanced much, I'll try to create a more comprehensive list.
James Durham on the Song of Solomon.
Joseph Caryl on Job
(Also Calvins sermons)
Calvin on the Psalms is pure gold.
William Greenhill on Ezekiel -- It's not modern and scholarly: but it's hard to beat.
Bruce Waltke on Proverbs and Micah.
E.J. Young, on Isaiah
Calvin is also particularly good on this book.
Deuteronomy: there are good commentaries on this book, but Calvin's Sermons (not his commentary) are unbeatable.
King, on Jonah (with the same caveat as Greenhill)
Candlish on Genesis is priceless.