I've already covered some topics on Wicca and religion, but now I think I should more specifically focus on witchcraft and religion. Because, you must know by now that Wicca and witchcraft are not the same thing. If that is a surprise, you need to read a few more pages around here.
Anyway, is witchcraft a religion? I know that there isn't a solid answer about this and I probably will contradict other Pagan writers on this subject. This is my personal interpretation and I do know that many others follow this approach, even if not everyone.
Witchcraft is not a religion, though it can be a vital part of any spiritual path such as Wicca, shamanism or Voodoo. By itself, it is a magickal practice, much like Tarot reading. Drumming or dancing may feel very spiritual and it might bring you closer to the Universe or Deity, but it is not a religion in itself. These are all practices that can be part of any religion, whether a well-known Pagan one or a personal path that has no specific name.
According to Dictionary.com, religion is defined in part as:
1. a set of beliefs concerning the cause, nature, and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs.
As you can see, one of the key points of any path being a religion is that inclusion of beliefs rather than just practices. There is no real belief system in witchcraft, other than the belief that it works. That's the same as prayer in many ways, and prayer by itself is not a religion.
People often use the existence of a Deity to establish what is religion and what is not, but that's not really accurate. Even mainstream religions like Buddhism are Deity-free. So don't base your work with the Gods or Goddesses (or lack of it) as a way of defining your own faith.
You might find that your practice of witchcraft and your underlying faith in it are too intertwined to say they are separate, and I'm certainly not going to argue though I do disagree.