TkIspell

 What: TkIspell
 Where: ftp://ftp.slac.stanford.edu/software/TkMail/tkispell-4.0.tar.gz   ???
 Description: Interface to ispell command. Version 4.0 is intended to
        work with Tk 8.x. Comes with two utility files that can
        be sourced in to provide spell checking abilities in other
        Tk programs.
        Currently at version 4.0.
 Updated: 07/2007
 Contact: See distribution package

Once was part of Paul Raines's TkMail application. The original site, above, no longer appears to be available.