Accessible and easily installable hunspell dictionaries. Useful with, for example, nodehun.
See each of the below packages for installation guidelines.
Each dictionary can be installed on OS X by following this StackExchange answer.
New dictionaries can be added quite easily. Most importantly, they must be licensed with an Open Source License, and they should be convertible by iconv(1) to UTF-8.
See LICENSE files in each dictionary for the licensing of index.dic and
index.aff files.