Satanism is a religious, semi-religious and/or philosophical movement whose adherents recognize Satan, either as an archetype, literal being, pre-cosmic force, or anything inbetween. Some Satanists celebrate aspects of human nature represented by the usually Christian or literary (Milton, Goethe) Satan archetype. Many Satanists do not worship a deity called Satan or any other deity. Unlike many religions and philosophies, Satanism generally focuses upon the spiritual advancement of the self, rather than upon submission to a deity or a set of moral codes. However, some Satanists do have moral codes, e.g., the 9 Statements or 11 Laws of the LaVeyan Satanists.
It should be noted that the depiction of so-called "Gothic Satanism" is not actually known to be practiced in the world today. This is the Satanism accused during the Inquisition, with tales of murder and baby-eating.
Many contemporary Satanists eschew traditional religious beliefs, attitudes and worship in favor of a more egotistic worldview and practices such as magick. Groups or individuals described in some sense or another as Satanic can largely, though incomprehensively, be described as belonging to one of two unofficial sub-groupings: Philosophical Satanism or Religious Satanism.
http://en.wikipedia.org/wiki/Satanist
Sa·tan·ism (stn-zm) KEY
NOUN:
The worship of Satan characterized by a travesty of the Christian rites.
satanism Profound wickedness.
http://education.yahoo.com/reference/dictionary/entry?id=s0096200
LaVeyan Satanism is a religion based upon the philosophy of Anton LaVey as outlined in The Satanic Bible and other works.
Philosophically, it could be described as heavily influenced by the writings of Aleister Crowley, Niccolò Machiavelli, Friedrich Nietzsche, Ayn Rand, Ragnar Redbeard, Sigmund Freud and a few others; "Satan" is appropriated as a positive symbol of this worldview, and is not considered to exist in a literal fashion.
http://en.wikipedia.org/wiki/LaVeyan_Satanism
More reading in the above link. but here is a few that I thought was worthy of noting:
From "The nine Satanic statements":
#5 Satan represents vengeance instead of turning the other cheek!
#8Satan represents all of the so-called sins, as they all lead to physical, mental, or emotional gratification!
From "The eleven Satanic rules of the Earth":
#4 If a guest in your lair annoys you, treat him cruelly and without mercy
#11 When walking in open territory, bother no one. If someone bothers you, ask him to stop. If he does not stop, destroy him.
Here is the man that they follow?
Anton Szandor LaVey