Freemasonry is a lodge, not a religion. They are no more "Satanic" than a college fraternity, the Elks Club, Knights of Columbus, or the American Legion. You can go look up a local Freemason chapter in the Yellow Pages, walk into the building, and ask more about them.
As for Satanism, well there are a number of different practices that the media and Christian zealots label with that term. But as for an actual organized religion called "Satanism" with practitioners that actually identify THEMSELVES as "Satanists", that didn't exist until the formation of the Church of Satan
in the 1960s by Anton Szandor LaVey, who later wrote out the principles of the religion in "The Satanic Bible". Some people claim otherwise, but I have yet to see any historical evidence for their claims.
The Church of Satan
has certainly had a few famous members: Sammy Davis Jr., Marilyn Manson, Jane Mansfield, etc. There are other famous celebrities and politicians who are Satanists, but they keep their affiliation a secret, knowing that it would be career suicide to be out-of-the-closet about it.
As far as beliefs go, Satanism is a religion of the flesh, rather than the spirit. It's a strictly non-theistic philosophy that embraces concepts such as self-importance, self-responsibility, critical thinking, justice, humor, indulgence, and host of other things that other religions have traditionally branded as "evil". We use Satan as a symbol and convenient archetype for those values.
As you can see from some of the other responses here, a lot of idiots claim to know what Satanism is without doing even a minimal amount of research on the subject first. They largely get their false information from tacky horror movies and sensationalist talk show hosts.
"Theistic Satanism" is an oxymoron. Satanism is non-theistic; we believe the whole notion of deities is an invention of the human mind. There's already a name for people who believe in an actual Devil and worship him: they're called "devil worshipers".
Some people are mentioning Aleister Crowley and Charles Manson. Neither of them ever claimed to be Satanists, and no educated person that I know of considers them to be Satanists either. Crowley established a completely different religion called Themela, and Charles Manson was just a criminally insane cult leader.