Since Pharmboy brought Kabbalah up, can I as you something just because I'm really curious. How popular is Kabbalah among Jews? It seems to be well accepted at JewishWorldReview.com.
'Kabbalah' means 'that which is received'. Specifically, it usually refers to the collected teachings of Isaac Luria. Hassidism (Chabad/Lubavitch is the most well known branch of Hassidism) is practical applied kabbalah.
It is difficult to find traditional Jewish literature that does not make reference to kabbalistic concepts.
Kabbalah as an inseparable part of Judaism is not the same as the Hollywood mysticism which uses the same name.
Kabbalah is Jewish mysticism. Technically, though, because of the potential for spiritual corruption, you are not supposed to study it unless you are a 40 year old + religious male. It contains truths that are dangerous is improperly understood, or abused. It is an important part of Judaism, but not for the idly curious. At least in theory. Names of angels, or the nature of physical manifestations of evil are not appropriate for everyone to study.
If you want an example of the harm it can do in the wrong hands, just look at many occultist and New Age practices of sorcery. Many beliefs and practices stem from improper use and abuse of Kabbalah.
In the right hands, it's a very helpful, perhaps even critical, tool for a deep understanding of Judeo-Christian beliefs. So much so that the Catholic Church and many faithful Christians take a look at it to get a better grip on their own faith.