According to Slashdot, Sarcasm, Inc., is trying to advocate a new punctuation symbol to indicate sarcasm, the SarcMark, only they have copyrighted it and require the purchase of their software to use the symbol. Open Sarcasm has responded to the SarcMark by providing an open sarcasm symbol: ¡. Yes. It's an upside down exaclamation point (I have no idea what the official name for the typographic symbol is. Anybody?).