Thanks in no small part to 70s and 80s horror flicks, the pentagram seems to have become largely misunderstood. In Neopagan/Wiccan traditions, it's regarded as a very positive symbol and has a looooong history. Christians believed it symbolized the five wounds sustained by Christ, and Neopagans/Wiccans view it as the unification of the four elements--earth, air, fire, water--and the human spirit, or Akasha. Generally speaking, when enclosed in a circle, it's called a pentacle (though 'pentagram' and 'pentacle' are often used interchangeably).
The underlying key to the misunderstanding is probably that when inverted, the pentacle represents the elements and Akasha turned on their heads, and as such was commandeered as a symbol by those who chose/choose to exploit the more animalistic, darker aspects of our existence. The inverted crucifix is in the same boat. The upright pentacle is a truly beautiful and unifying symbol, and is meant to highlight how our spirits exist in harmony with the elements of the universe. The pentagram represents wholeness and perfection (particularly in its representation of the four elements and Akasha), aspects that have made it popular in magic work . It was also a popular symbol among followers of Pythagoras and, for them and for others, was and is a sign of well-being and good health. Speaking of good health and pentagrams, cut open an apple in half: you'll find a pentagram hovering around the seeds! It's not an accident that this shape and the apple are related in terms of longevity and health.
There are four suits in the Tarot, one of which is Pentacles (though Pentacles, in some decks, become Discs, Coins, or even Stones). The suit of Pentacles is related to earth and represents what we have: money, health, property, and the like, but the general image of the pentacle does not give the elements any sort of hierarchy--the five points are all equal, one no more important or less significant than the next, with Akasha as the center point at the top. When you see this symbol, try to form an image in your mind of the beauty of what it represents. It can become a very powerful visual!
P.S.: Despite the dissemination of an unbelievable amount of misinformation about earth-centered religions in old (and recent!) horror movies, I still love 'em. :-)
