Translation of labels via TypoScript

Translations for frontend extensions normally are placed in the file pi1/locallang.php. If the language needed is not defined you should send your translation to the maintainer of the extension. I think most of the time they will include it to the next version. If you edit the file for yourself there might be the risk of overwriting your changes with the next update of the extension (if your translation was not included by the maintainer). So before editing locallang.php and also in some other cases it makes sense to define or even overwrite (in case the current translation doesn't suit you) the language via TypoScript. For jk_poll this might look something like that:

plugin.tx_jkpoll_pi1 {
 _LOCAL_LANG.de {
  submit_button = beliebiger Text
  votes_total = anderer Text
 }
 _LOCAL_LANG.en {
  submit_button = some text
  votes_total = another text
 }
}

I think the changes you have to make for other extensions are quite obvious. You have to change the extension key ('tx_jkpoll_pi1' in this case) and find the right labels in locallang.php. The language is defined with '_LOCAL_LANG.de' and '_LOCAL_LANG.en'.