I've found the following resources helpful. In some cases, newer editions are available.
Abbreviations for each resource are enclosed in parentheses and used elsewhere on this website.
Study Bibles
Study Bibles contain subject indexes, cross-references, book summaries, maps, diagrams, pictures, archaeological discoveries and gold mines of explanatory footnotes. They are among the most valuable long-term investments you can make.
Footnotes in major study Bibles are often the result of team efforts and may have undergone more scrutiny than single-author commentaries. To reduce bias and increase the likelihood of finding an answer to your particular question, it's good to have more than one study Bible at your fingertips. All of the following are available for the Olive Tree Bible app. The notes can be made to scroll along in a parallel window with your Bible text, and you can quickly switch between resources to see the diversity of comments on the passage you are reading.
(ESVSB) ESV Study Bible, © 2008 by Crossway Bibles. It uses the text of the English Standard Version (ESV).
(HCSBSB) HCSB Study Bible, © 2010 by Holman Bible Publishers. It uses the text of the Holman Christian Standard Bible (HCSB).
(LASB) Life Application Study Bible, NLT, © 2007 by Tyndale House Foundation. The master index at the end doubles as a good subject index. It uses the text of the New Living Translation (NLT).
(NET) New English Translation, ©1996-2017 by Biblical Studies Press, L.L.C. Also available with full notes at BibleGateway.com.
(NIVCBSB) NIV Cultural Backgrounds Study Bible, © 2016 by Zondervan. It uses the text of the New International Version (NIV).
(NIVSB) NIV Study Bible, General Editor Kenneth Barker, © 2011 by Zondervan. It uses the text of the New International Version (NIV).
(NIVZSB) NIV Zondervan Study Bible, General Editor D.A. Carson, © 2015 by Zondervan. It uses the text of the New International Version (NIV). In 2018 this resource was reprinted and renamed to be the NIV Biblical Theology Study Bible.
(NKJSB) NKJV Study Bible, 2nd edition © 2008 by Thomas Nelson. It uses the text of the New King James Version (NKJV).
(NLTSB) NLT Study Bible, © 2008 by Tyndale House Publishers, Inc. It uses the text of the New Living Translation (NLT).
(RSB) The Reformation Study Bible NKJV, © 2016 by Reformation Trust Publishing. It uses the text of the New King James Version (NKJV).
Stand-alone commentaries
Commentaries can be massive and expensive, sometimes requiring 20 or more volumes to cover the whole Bible. The following are smaller, less expensive, and written to be accessible to laypeople.
(BKC) The Bible Knowledge Commentary, An Exposition of the Scriptures by Dallas Seminary Faculty, Walvoord and Zuck. Two volumes: Old Testament © 1985 SP Publications, Inc.; New Testament © 1983 SP Publications, Inc. This can also be purchased for the Olive Tree Bible App mentioned further down.
(BibleRef) https://www.bibleref.com, Type the reference for a Bible verse into the search window and see a commentary and the full text of the verse in multiple translations. Not all parts of the Bible are yet available. The site is growing.
(BEC) The Bible Exposition Commentary, Warren W. Wiefsbe, Published by David C. Cook. Don't let the six-volume size frighten you. It's very readable by laypeople. If you shop around, you just might be able to find the entire set for about $80 (US).
Old Testament, Genesis-Deuteronomy, 460 pages. © 2001, Warren W. Wiersbe
Old Testament, Joshua-Esther, 751 pages, © 2003, Warren W. Wiersbe
Old Testament, Job-Song of Solomon, 551 pages, © 2004, Warren W. Wiersbe
Old Testament, Isaiah-Malachi, 489 pages, © 2002, Warren W. Wiersbe
New Testament, Matthew-Galatians, 728 pages, © 1989, Warren W. Wiersbe
New Testament, Ephesians-Revelation, 626 pages, © 1989, Warren W. Wiersbe
(ABC) Africa Bible Commentary: A One-Volume Commentary Written by 70 African Scholars. Produced by African biblical scholars, in Africa, for Africa—and for the world. Passage by passage commentary. Includes more than 70 special articles dealing with topics of key importance to ministry in Africa today, but that have global implications. Zondervan (2010), 1632 pages. Available in hardback and Kindle editions.
(SABC) South Asia Bible Commentary: A One-Volume Commentary on the Whole Bible. All authors are scholars writing from within their own contexts for the people of South Asia. Articles are written within the confines of the Lausanne Covenant and all contributions are in line with and support the confessional direction of the Lausanne Covenant. Zondervan (2015), 1824 pages. Available in hardback and Kindle editions.
Bible dictionaries
After your study-Bible(s), a good Bible dictionary may be your most helpful tool.
Bible dictionaries are helpful for reading about the historical, physical, and cultural setting. Look up subjects alphabetically for background information on names, places, people groups, holidays, occupations, agriculture, animals, biblical words, customs, cultures, and much more. If you can only afford one book other than a study Bible, this might be a good choice.
In my opinion, when it comes to Bible dictionaries, bigger is better. After all, you want your topic of interest to be in there when you need it. It also helps to have a reasonably up-to-date version, as new archaeological discoveries are being made all the time.
(HolmanDict) Holman Illustrated Bible Dictionary, © 2003 by Holman Bible Publishers, 1717 pages. At the time of this writing, it's one of the largest, most comprehensive English Bible dictionaries available.
Bible study websites
(BibleGateway) https://www.biblegateway.com. See up to five Bible translations side-by-side comfortably on your laptop. Access Bible translations, Greek and Hebrew lexicons, commentaries, Bible dictionaries, concordance, and other references.
(BibleHub) https://www.biblehub.com. View Hebrew or Greek interlinear with English. Type in a verse reference and see multiple translations, Greek and Hebrew lexicons, cross-references (TSK), commentaries, and Bible dictionaries on a single page.
(BlueLetter) https://www.blueletterbible.org. View clickable Strongs numbers embeded in the Bible text (when using KJV or NASB only). Access Bible translations, Greek and Hebrew lexicons, cross-references (Treasury of Scripture Knowledge, TSK), commentaries, Bible dictionaries, and other references.
(Bibleis) https://www.bible.is. On this website you can view the Bible in hundreds of languages. You can also hear audio recordings of Scripture in many languages. Some of the audio presentations are dramatized to include different voices for different speakers, sound effects, and music. Some versions even have parallel video scenes. You can use Bible.is online or obtain the stand-alone app.
(BibleRef) https://www.bibleref.com, Type the reference for a Bible verse into the search window and see a commentary and the full text of the verse in multiple translations. Not all parts of the Bible are yet available. The site is growing.
(OpenBible) https://www.openbible.info/topics. An interesting Internet subject index that grows as users make contributions. The verses for each subject are placed in order by the number of "helpful" votes that come from users.
(BibleOrg) https://bible.org. Provides easy access to the NET Bible translation with over 60,000 footnotes. Look up keywords, topics, and study helps. Find links to other sites with related information.
(GotQuestions) https://www.gotquestions.org. This website answers more than 700,000 Bible questions.
Software (Apps)
Download these once, then use them without needing continued Internet access.
Using software like this, the average person today has access to more tools than many pastors had even 30 years ago. The most recent developments are for smart phones and tablets. Now you can carry your study Bibles, Bible dictionary, and other tools right in your pocket. Many software packages are available. Below are the ones I know best. (I do not currently recommend purchasing Bibles for standard electronic book readers. Dedicated Bible apps have Bible exploration tools that book readers don't.)
(OliveTree) Olive Tree Bible App: https://www.olivetree.com/bible-study-apps. Bibles and Bible resources for iOS, Mac, Windows, Android, and other platforms. Free and for-purchase modules are available. ALL of the study Bibles listed above as well as the Holman Illustrated Bible Dictionary and the Bible Knowledge Commentary can be purchased for this app. Footnotes and commentaries can be made to scroll along with whatever Bible version you are reading.
(Bibleis) Bible Is App: https://www.bible.is. You can download apps for Mac, Windows, iOS et Android. View the Bible in hundreds of international languages. Hear audio recordings of Scripture in many languages. Some of the audio presentations are dramatized to include different voices for different speakers, sound effects, and music. Bible.is continues to add new Bible translations, and they now have video accompaniment for a few of these. You can also use Bible.is online without obtaining the app.
(OLB) Online Bible App: https://www.onlinebible.us. For years, this was my Bible app of choice. I still use it from time to time, but the Mac version no longer works well on the more recent versions of MacOS, and no updates are being offered.
A few books on grammatical historical hermeneutics
Understanding and Applying the Bible, Robertson McQuilkin, 2009, Moody Publishers, 382 pages.
Knowing Scripture, R. C. Sproul, 2009, InterVarsity Press, 152 pages.
Hermeneutics: Principles and Processes of Biblical Interpretation, Henry A. Virkler and Karelynne Gerber Ayayo, 2007, Baker Publishing Group, 256 pages.
Grasping God's Word, A Hands-On Approach to Reading, Interpreting, and Applying the Bible, Duvall and Hays, Published by Zondervan, Third edition © 2012 by Duvall and Hays, 506 pages. (Written for serious readers, especially college and seminary students.)
Exegetical Fallacies, D. A. Carson, published by Baker Academic, Second edition © 1996, D. A. Carson, 160 pages. (Written for preachers and teachers of Scripture)
The Hermeneutical Spiral, A Comprehensive Introduction to Biblical Interpretation, Grant R. Osborne, Published by Inter Varsity Press, Second edition 624 pages, © 2006, Grant R. Osborne. (Written for pastors and teachers)
Other books you may find helpful
Instruments in the Redeemer's Hands - People in Need of Change Helping People in Need of Change, Paul David Tripp, 2002, P&R Publishing, 362 pages. This is not a book about Bible interpretation but about applying the Bible to the trials of life. In the first five chapters, Tripp shows the reader how to draw counsel from the Bible for their own life. Chapters six through fourteen empower the reader to help others.