Today I created package with Polish regional settings for Maemo OS2008. They are working and show as “Polski (Polska)” in “Control panel -> Language and region”.
I used glibc 2.5 locale data + Ångström localedef and generated locale files on my N810. To make them appear as “Polski (Polska)” instead of “pl_PL” I edited LC_ADDRESS file like it is described on “i18n add new languages” Maemo wiki page.
When I will make more Polish addons I will probably create repository with it (another one ;(