Hunspell is the default spell checker of OpenOffice.org and Mozilla Firefox 3 & Thunderbird.(http://hunspell.sourceforge.net/)
For Firefox 3 we are using an aspell dictionary which was moved to hunspell.
In aspell the biggest problem was to create the .AFF file which contains rules for words. With this the .DIC file can contain fewer words. Not sure how this works, or how hunspell deals with the same issue.
The dictionary we are using now was made by Taras Bendik in 2003 for the Macedonian version of OpenOffice.org 1.x.
The current (and only) XPI:
Links on creating affix files: