I was just messing around with Google Sites and noticed that as soon as I made my site the homepage had a PR of 9 (before it crosses your mind all the links it makes are nofollow).
The homepage of the test site I was playing around with is https://sites.google.com/site/samsnewsite030413/
Why does this happen as PR is on a per-page basis, and as the page is brand new how does it have a PR? I've seen a similar thing happen with Github project pages; they seem to have a PR8 as soon as they are made, it's not like they are running off a standard URL with JavaScript bringing in the content - they seem to be static pages with their own URLs.