JohnMu from Google posted a blog post named Working with multi-regional websites. The post goes over many of the SEO implications behind making multiple web sites all targeting different regions around the world.
John discusses URL structures, hosting, domains, using Webmaster Tools and much more. If you ever had to deal with a multi-regional web site before, this post is something you should read. It does not however fully cover multi-lingual issues, but a post on that is coming soon.
The beauty of this post is that it is living over in the Google Webmaster Help forums. John is there answering additional questions that were either confusing or not clear to readers. So if you have additional questions, hit up the forums.