While a lot of Office 365 administration can be done from the web interface, there are still a fair number of things that require PowerShell. One of these things is delegate management (though this is something that can also be handled via Outlook, but not OWA).
I wrote a small application the allows you to easily add permissions as needed, and it should work for Office 365 or Live@Edu. While it doesn’t read any existing permissions, it allows you to specify delegate permissions or grant Send As/Full Mailbox access so long as you have an administrator account. The application (and full source) is attached. A screenshot that should give you a good idea of what it does is below.