Sites is the Google version of wikis within Google Apps for Education.
Being within the Apps domain, permissions are very easily managed. With groups of users previously set up, permissions can be set at three levels - we have called these "A", "N" and "P".
It is possible to share the site with everyone ("A" for all):
If you want to restrict it to all your users in your apps domain, then there is a box to check to do that - and you can choose to allow edits or just viewing.
And finally, you can invite members of your domain to be "owners", "collaborators" or "viewers" ("P" for obvious reasons).
We have placed all our documentation on-line using sites, with permissions accordingly.
Embedding within sites works well. It is also possible to embed Google docs and forms within the site (but remember that the permissions have to match the site ones).