There are books you can get that give the general idea of an "introduction". One I read not too long ago was simply entitled "Satanism" by Brother Nero; it gives a good general outlay of the philosophy behind Satanism, or at least, Nero's opinion on it. While I disagreed with certain things in it (I'm not a Theistic Satanist, so, I'd be almost bound to) I still consider a good introduction. Having spoken with Nero since reading it, a "Book 2" was in the works to help outlay things like further philosophy and ritual, but as I can recall, it was scrapped once the publishing company that published "Satanism" went down the plug.
I would also recommend doing some research. Also, keep in mind that there are several different type of Satanism, including the Church of Lucifer and many different sub-cults. I would recommend going to a Barnes and Noble and checking the New Age section. I myself have found a few interesting books on the subject. From there, you can expand your search if you so choose.
If you're going to pick a website, my favoured one is simply called "theisticsatanism". The website is layed out much better than JoyofSatan, and it seems to be written in a much more "professional" sense. Just my two pence.
I don't know any teachers or sites other than joysofsatan.com and thechurchofsatan.com. I would also like some help with these subjects but I will offer you the knowledge I have gathered so far. The Lavey satanists follow the teachings of Anton Lavey(sorry if that was misspelled) which he wrote down in a book called The Satanic Bible. They do not worship Satan but use him as a symbol for their humanistic views. Most of them are atheists from what I gather. I haven't been able to gather information on the other branches due to location and the fact that no sources would tell me their beliefs. I'm sorry if I wasn't helpful or got any information wrong. It was all gathered from other sources and I can't testify as to weather it is true or false.
