GNU Spell, a clone of Unix `spell'

 GNU Spell is a spell checking program which prints each misspelled word on a
 line of its own. It is designed as a clone of the standard Unix `spell'
 program, and implemented as a wrapper for Ispell. Spell accepts as its
 arguments a list of files to read from. Within that list, the magical file name
 `-' causes Spell to read from standard input. In addition, when called with no
 file name arguments, Spell assumes that it should process standard input.