I'm developing a solution integrating CRM Online with Sharepoint Online and requires to do some custom work from CRM Online plugin (sandboxed) to access Sharepoint Online Web Service.
Thus, claims based authentication is required, but I haven't found any solution which doesn't use WIF: http://blogs.msdn.com/b/cjohnson/archive/2011/05/14/part-2-headless-authentication-with-sharepoint-online-and-the-client-side-object-model.aspx
(because CRM online plugins is sandboxed and doesn't allow using Microsoft.Identity.Model.dll).
Have you found a solution to this issue? I am on the same boat, need to be able to connect to Sharepoint 365 from a CRM Online Plugin.
I ended up deploying an Azure Web Service as middle ware to implement the claims based authentication.
I have raised a support ticket to Microsoft, and they can't provide with a solution as well, looks like this would be the only way so far to accomplish the integration.
I also ran into this situation. I was able create a CRM plug-in that called SharePoint web services using the following instructions (both CRM and SharePoint are online)...
In my solution, I created an HttpWebRequest for steps 1 & 3. The contents of the request are manually created using the format described in the blog.