Google Sites is offering 10GB of extra storage. With Google sites you can create wiki style web pages with out learning any html. You will be presented a rich text editor where you can add elements, text, links and other Google application. You can add Google docs, spreadsheets, youtube videos, google videos, calender, gadgets etc to the pages.
This feature is not enabled by default in Google Apps accounts, to enable it click on “Add more service” link in your dashboard and select Google Sites. Once you enable it you can create sites.
Users can set the permissions to the pages as who can access those pages.
There are a few themes available as of now to select for your pages. There are not many customization options for selecting page layouts etc. But the collaboration features are good and it is easy to use. Source: Webware