If you want your favourite application to support your language or fix some localization errors
feel free to register and make your contribution into development. Registration is free and fast - you need only to provide your email (which will be used only in case of some problems with translations or password reset). When you log in you will see the list of languages which are available for localization. For each language you can see current localization status - and if its not perfect feel free to click on it and see which lines are not perfect there. If you have time to localize only few lines it is still great help.
While localizing keep in mind the length of strings - user interface migth not support very long labels. Localized string will have special "too long" sign to indicate the label needs some shortening.