Over of the Windows Azure blog there have been some cool announcements, http://blogs.msdn.com/b/windowsazure/archive/2012/09/12/more-advances-in-the-windows-azure-active-directory-developer-preview.aspx.
I’ve been using https://activedirectory.windowsazure.com for a while now and with the announcement of “standalone tenants” this presents huge possibilities. In hosting circles I have often had discussions for providing “multi-tenant” AD available on demand, but have always come to the conclusion it would require Microsoft to make some key changes.
Check it out now, http://windowsazuire.com.