Foul language

I want to ask our English/American-speaking forum readers and writers about foul language.

Could you be so kind as to point me some good links to “theoretical reference”, please? 🙂
Next question is about usage – where is the limits? Are F-words THAT really bad?
What about “damn”, “sh1t”, etc.?
What about you/your children – use it or not?
What is your own point of view about the subject?
What do you think about usage of explicit/foul/obscene language in films (there are a lot of)? Is it OK? How do you feel whatching “Pulp fiction” or “Snatch” just for example?

My question is related with films, books and other cultural/sub-cultural products in order to find proper equivalent with Russian. There are a lot of opinions about such correlation, so I’d like to know your opinion.

Thanks in advance.

PS.
What about this books
English As a Second F*cking Language by Sterling Johnson (Paperback)
Forbidden American English by Richard A. Spears (Hardcover)
Slang and Euphemism: A Dictionary of Oaths, Curses, Insults, Sexual Slang and Metaphor, Racial Slurs, Drug Talk, Homosexual Lingo, and Related Matte by Richard A. Spears (Hardcover)
?