The ChinaSmack website offers a regularly-updated list of "common Chinese-language internet terms, expressions, acronyms, and slang" so non-Chinese speakers can better understand funny or offensive language used by Chinese speakers on and offline.
Valuable things I have already learned from this website, even by focusing solely on the list items that do not include Chinese characters: "3P" means a threesome. "BT" means perverted. "JJ" and "J8" refer to male anatomy, while "JC" refers to cops. Also: "Human Flesh Search Engine"? Yeah.
Think I'm all set to cruise the messageboards now.