Hunspell is a spell checker and morphological analyzer library and program designed for languages with rich morphology and complex compounding or character encoding. Hunspell interfaces: Curses, Ispell compatible pipe interface, OpenOffice.org UNO module
There are a lot of useful features. Documentation is small but accurate. Some reviewers apperently did not take the time to dive into the docs. Some of the dictionaries are lagging behind. Some affix files are made too complex to uderstand easily. Nevertheless a perfect tool.