Easy way to install additional spell-check dictionaries for OS X?
Mac OS X is compatible with the aff/dic open format dictionaries.

All you need to do is to get one dictionary, and place it inside ~/Library/Spelling (you may have to create the directory).


Get the Romanian dictionary from OpenOffice (or search for another language)
Extract the file using The Unarchiver or rename the extension to .zip and extract it
Move the files with the .aff and .dic extensions (ro_RO.aff and ro_RO.dic for Romanian) to your ~/Library/Spelling folder.
Go to System Preferences > Keyboard > Text > Spelling  and choose the language of your choice
...boom! you have system-wide spell checking :)