The STEP Bible (STEP stands for “Scripture Tools for Every Person”) is a free digital Bible software project run by the Bible and religious book publisher, Tyndale House. The underlying software powering the project is based on the popular open source SWORD Project managed by The Crosswire Bible Society. Many volunteers, publishers, Bible societies, and others participate by working and/or donating translations, tools, commentaries, interlinears, dictionaries, and other resources to the STEP Bible.
There is a vast array of easy-to-access tools for scholars as well as the average Bible reader like you or me. There are dozens of English translations and commentaries in addition to dozens of ancient language versions (great for the scholars among us). You can easily research multiple translations in modern languages (including both the NIV and ESV as well as many others), mouse hover Hebrew/Greek/Aramaic original words behind the translations, definitions, cross references, commentaries, original language grammatical help, interlinears, and concordances in original languages as well as modern languages. I was very impressed with how easy it was to use and at the extremely organized and well-designed user screens. There is generous use of popups so that you remain on the screen you’re already working on as much as possible. You can easily look up every instance of a Greek or Hebrew word in both directions (e.g., every time the word “love” is used and the different Greek and Hebrew words translated as “love” in your English translation OR every time the Greek word “agape” is used in English (even when it’s not translated into English as “love”).