Remo and mlocati have been working very hard on transifex and github to improve the support for multiple languages in the last few months.

There's more langauges complete than I can count:
http://www.concrete5.org/developers/translate/...


There's a debate on how those should be included with the core, all packed up and pickable from a drop down (my view) or with a hook to always download the latest from transifex on install (others suggesting as its more light weight and always up to date)

http://www.concrete5.org/developers/pro-accounts/community-leaders-...

Either way there is a strong desire to have a "pick your language" on install.

Thanks for the reply Franz :)