ispell – Multi-platform spell checker
Ispell is a fast screen-oriented spelling checker that shows you your errors in the context of the original file, and suggests possible corrections when it can figure them out. Compared to UNIX spell, it is faster and much easier to use. Ispell can also handle languages other than English.
Ispell is now largely superseded by aspell, a package that seasoned ispell users will find a comfortable home.
Free license not otherwise listed, or more than one free license applies
TeX-aware spelling checker
Maybe you are interested in the following packages as well.
- amspell: ASCII and LaTeX spell checker
- fourspell: Windows32 spell checker for TeX, RTF, HTML, and BibTeX
- excalibur: Macintosh spell checker
- spelling: Support for spell-checking of LuaTeX documents