"The number of languages used on the International Space Station has recently increased. In addition to those spoken in the 15 countries that have had representatives aboard the space station, American Sign Language, or ASL, is now included. NASA astronaut Tracy Caldwell Dyson has sent a message in ASL from the station to the deaf community."
Keith's note: As a former professional Sign Language interepreter myself (mid-70s to early 80s), stories like this certainly get my attention. As such, I do not mean to detract from this but, this is not the first time that an astronaut has signed a message in space for use back on Earth. It may well be the first video downlinked live with signing, however. According to Bill Readdy, he signed a short message on STS-42 back in 1992 (see YouTube video from CollectSpace below). The was not downlinked live but It was recorded and later appeared on a Gallaudet University's TV show "Deaf Mosaic". Bill still remembers some of the signs to this day. That said, this recent video is cool and is exactly the sort of thing NASA should be encouraged to do in the future so as to broaden its ability to interact with all citizens.