GNU Aspell is a Free and Open Source spell checker designed to eventually
replace Ispell. It can either be used as a library or as an independent
spell checker.
Its main feature is that it does a much better job of coming up with possible
suggestions than just about any other spell checker out there for the English
language, including Ispell and Microsoft Word. It also has many other technical
enhancements over Ispell such as using shared memory for dictionaries and
intelligently handling personal dictionaries when more than one Aspell process
is open at once.