Background information about the people, places, cultures, and historical events related to a passage.
Bible dictionaries will have short articles like "Revelation, book of," with overview-level information about the cultural and historical situation of the book and its audience. Start there, and then as you come across important people, places, etc. in your reading, look up other articles on those people/places/subjects (e.g., "Nero," or "Rome, early Christian attitudes to", etc.).
Commentaries also usually have some good background information. Look at the very beginning of the book in the introduction or background sections.
Once you've identified things you need to know more about (e.g., Nero's persecution of Christians, Israel's Babylonian exile, etc.), in addition to consulting the books below you can do a library search for books specifically about those subjects.
Sources to help you understand genre and structure, as well as see your passage in the context of its biblical book and the Bible as a whole.
Start by looking in a bible dictionary for articles similar to "Matthew, Gospel of" or "Job, Book of" for info on the genre, structure, etc. of a specific book. Then, look up articles like "Poetry, Hebrew," "Narrative Literature," or "Letters (epistles)" to get a broader introduction to a biblical genre.
Sources to help you look closely at words that are key to interpreting your passage.
Web sources like the ones below are good for quickly comparing translations to see which words are translated differently across English versions of the Bible. They can also be good for finding a Strong's number, or looking up a reference to a print source (e.g., TDNT, TWOT, etc.).
Websites like there are not useful for finding commentaries or Bible dictionaries/encyclopedias--commentaries included in these websites are usually between 100 and 500 years old!
Sources to help you with the overall anaylsis, interpretation and application of your passage.
Not all commentaries are the same. Some are meant to help pastors prepare sermons. Some are meant to help laypeople with devotional study. For exegesis, you'll want to use scholarly or exegetical commentaries. Some of the best series are listed below. These can be found in the university library's Bible Ready Reference Collection.
Use the ATLA Religion Databases Scriptures Tool to quickly search for all of the articles in the database that have to do with your passage. Learn How
For helping you in finding additional resources.