MySefer.com

MySefer.com‘s tagline is the “the largest online provider of Hebrew Sifrei Kodesh.” Nevertheless they also offer books in English, Yiddish, Russian and Spanish and French. Their English books on Kabbalah are from the following authors:

Rabbi Adin Steinsaltz
Rabbi Aryeh Kaplan
Rabbi Matityahu Glazerson
Rabbi Moshe Chaim Luzzatto (Ramchal)
Rabbi Nachman of Breslov
Rabbi Raphael Afilalo
Rabbi Yaakov Moshe Hillel
Rabbi Yitzchak Ginsburgh

As of now they have 134 books listed in this category, although some of those books are related to Kabbalah to a much lesser degree than others. But it’s a great source to get Religious Jewish works on the topic.