>I've seen the word "extropian" used in science fiction on three
>occasions: "Slant" by Greg Bear, "Voice of the Whirlwind" by Walter John
>Williams, and "Wang's Carpets" by Greg Egan. In the last two cases, the
>"Extropians" are a cult. In the first book, the "Extropians" are
>mentioned as justification by a member of a cult.
To that you can add Alexander Besher's "Mir", and its opening reference to the "Extropian Library of Congress". Only just bought the book and am still to read it, so I can't comment further.