InterVarsity Press and Easy English offer free online Bible studies on the book of Esther. Both websites include chapter-by-chapter commentaries, insights and study tools for individual or group studies.
InterVarsity's free study guide for Esther guides students to personal application of Biblical principles. It seeks to accomplish this through an outlined set of instructions for each chapter that direct the student to read the chapter. The chapter study provides three activities including discovering the Word, applying the Word and responding in prayer.
Easy English presents verse-by-verse commentaries in an academic style. Other tools include word studies and a Jewish calendar for the book of Esther.