We have a lot of non-english speaking members, so when MortyDice sent me a link of game achievements on xbox live in French, I wondered how easy it would be to grab them and add them to the system to assist our friends from overseas.
And the answer was - quite easy!
If you go to your Customize ->My settings page, there's now a language option in the Regional Settings.
Choose your preferred language, save your settings and then head over to any game page or achievement page - et voila!
Not all languages have good support on xbox live, but French, Spanish, German and Italian look like they have a lot of support. So you should find these foreign language versions of most games.
I haven't implemeneted them everywhere yet, so your friend feed and recent achievement lists will still be in English, but if it all works well I will add that this week.
There's a also been a couple of mods in the forums, you can now hover over a message thread title to see the first post, and there's a perma-link button on every post if you want to link to it from another site.