XING is the leading system in 'social network' systems (despite linkedin is more known in the US). It is available in 16 different languages. I understand that it automatically adopts to your language.
I have been registered for over a year now and I really like it because it is a great tool to stay in touch with friends and collegues internationally.They have high-quality boards for a lot of topics as well.
Basic functions are free and if you use this invitation link, I understand that you can use all of the functionality for a month if you follow an invitation link from a current member:.
If you would like to give it a try: http://www.xing.com/go/invita/3286452