Change system language I have a craft installation (that's up to date), that was installed with english as the system language. Now that Craft has quite a lot of system languages, is there a way to change to another language for the control panel?
If you're running Craft Personal or Client, you'll need to go to the craft_locales table in your database and change the locale to one of the support Craft control panel translations (http://buildwithcraft.com/help/cp-languages).

If you're running Craft Pro, you can go to Settings->Locales and add (and re-order) new locales to your site.  Then you can go to your user account settings and set your preferred locale from list of existing site locales and the CP will display in that.  Again assuming it's one of the locales that the control panel has already been translated into.