yes, religion has always been a powerful weapon in the wrong hands...
EDIT: Thinking about my own religion, its interesting. I am an eclectic Wiccan (meaning I do not fully adhere to the Wiccan religion, I mix it with some parts of other religions, and my own personal beliefs, i.e I celebrate Christian holidays such as Christmas and Easter, but I also practise spellcasting). Wicca actually has a means of self-regulation when it comes to people using religion to have power over others (ex. the Puritans and extremist Muslim Clerics). As we are not exactly an 'organised' religion, we do not have a leader, in the same way that Catholics have the Pope, for example. Therefore, the most people that any one witch could have power over would be a single coven, which is traditionally thirteen people, without resorting to means such as mind-control magic, which would have its own severe repercussions on the caster. (Certain branches of magic are forbidden, mind control among them). We do have people who are respected highly within the religion, these people tend to be authors, but their works are by no means considered to be definitive.
We do not have a bible; Wiccans create their own personal 'bible' detailing their spiritual journey through life. This is a highly personal book and is called a 'Book of Shadows'. It must be protected above all else, because in the wrong hands the contents can render the author vulnerable to an extent that only a complete reversal of their practise can protect against. My BoS is one of the few things on my computer that is permanently encrypted. Even the encrypted version is far from complete; it is mostly stored in my head.
We only have one 'commandment' as such, but it encompasses everything the Christian commandments do, and more. It is called the Wiccan Rede ('rede' is an old word meaning 'rule' or 'law') and it runs thus:
Wiccan RedeAn ye harm none; do what ye will, An it cause harm; do what ye must.
'harm' is defined as anything that has a negative effect on another being or the planet. In modern English, this means you can do anything that will not cause any harm in any shape or form, to any being or entity. This is extremely difficult, so we fall back on the second part: short-term harm is acceptable providing the good outweighs the bad. I.e harm for the greater good. Even this isn't easy, so Wiccans must carefully consider their intents and purposes before casting spells. Magic is not the answer to everything.
Now, you might be wondering, 'What happens if a witch breaks the Rede; there's no-one with authority to deal with them'. Yes and no. There is no being with authority, although if they are hell-bent on causing harm, other witches will use the second part of the Rede to take action against them. There is a more ethereal force at work, however. That is the Rule of Three, also known as the Threefold Law, the Karmic law, the Law of Threefold Returns, Karmic justice or a wide range of other names. Basically, this states the following: Whatever energy you send out, be it positive or negative, will return to you threefold. Hence good 'luck' and bad 'luck'. One major way of taking action against errant witches is to invoke a spell known as a 'three times three' spell, which forces the Law of Three to take immediate effect upon the wrongdoer, rather than waiting for when it happens naturally (which could be minutes or years or anywhere in between) This is a good spell to use in that case, because it cannot backfire on the caster. If the 'wrongdoer' has done no wrong, then it will reflect good luck on them. If they are still trying to cause harm after that, then a binding is usually cast, but bindings are dangerous and can easily backfire. Ironically, it is the Threefold Law that causes spells to backfire when they do.
We worship many Gods/Goddesses, which ones a Wiccan follows is up to the individual, I personally am attuned to Bast, the Ancient Egyptian cat Goddess (How many of you saw that coming? :P) and Hecate, the Goddess of magic and Witchcraft.
For those of you that were wondering, but were too afraid to ask; yes some witches do perform rituals 'nekkid', again that is personal choice, and it is referred to as 'skyclad'.
Since we Wiccans are very fond of the arts (that does NOT mean we are any good at them personally :P ), I'll finish this post with a poem/rhyme about Wicca :)
Bide the Wiccan Laws we must
In Perfect Love and Perfect Trust.
Live and let live,
Fairly take and fairly give.
Cast the Circle thrice about,
To keep the evil spirits out.
To bind the spell every time,
Let the spell be spake in rhyme.
Soft of eye and light of touch,
Speak little, listen much.
Deosil go by the waxing moon,
Chanting out the Witches’ Rune.
Widdershins go by the waning moon,
Chanting out the baneful rune.
When the Lady’s moon is new,
Kiss the hand to her, times two.
When the moon rides at her peak,
Then your heart’s desire seek.
Heed the North wind’s mighty gale,
Lock the door and drop the sail.
When the wind comes from the South,
Love will kiss thee on the mouth.
When the wind blows from the West,
Departed souls will have no rest.
When the wind blows from the East,
Expect the new and set the feast.
Nine woods in the cauldron go,
Burn them fast and burn them slow.
Elder be the Lady’s tree,
Burn it not or cursed you’ll be.
When the Wheel begins to turn,
Let the Beltane fires burn.
When the Wheel has turned to Yule,
Light the log and the Horned One rules.
Heed ye Flower, Bush and Tree,
By the Lady, blessed be.
Where the rippling waters go,
Cast a stone and truth you’ll know.
When ye have a true need,
Hearken not to other’s greed.
With a fool no season spend,
Lest ye be counted as his friend.
Merry meet and merry part,
Bright the cheeks and warm the heart.
Mind the Threefold Law you should,
Three times bad and three times good.
When misfortune is enow,
Wear the blue star on thy brow.
True in Love ever be,
Lest thy lover’s false to thee.
Eight words the Wiccan Rede fulfill:
An ye harm none, do what ye will
Blessed be :)