Found this on Digg, it's a little site where you type what you want to say, and it will come back upside down and you can copy and paste it
˙pǝɹoq ǝɹ,noʎ uǝɥʍ op oʇ ƃuıɥʇǝɯos 'ʇɐǝu ʎʇʇǝɹd s,ʇı
˙ƃuıʎɐs ǝɹ,noʎ ʇɐɥʍ ʇno ǝɹnƃıɟ ʎǝɥʇ sɐ ooʇ ǝɯıʇ sǝldoǝd ɹǝɥʇo ƃuıʇsɐʍ ɹoɟ pooƃ
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