Or HaSulam Online from the Ashlag Heritage Foundation is a comprehensive platform for searching and studying Kabbalah. It includes a glossary, a subject index of kabbalistic concepts, a complete library of the published and unpublished writings of The Ari-Rabbi Yitzchak Luria, an audio and video library related to his work and that of other commentators on the Kabbalah and a store from which you can order material.
Glossary of Kabbalah
From the Bnei Baruch World Center for Kabbalah Studies comes this glossary of kabbalistic terms in browsable form. A Hebrew-Hebrew version of the glossary is also available.