As I alluded to in an earlier post, there have been some changes in SP1 and June CU that impact the ability of Windows Phone 7 (both RTM and Mango) and other mobile devices to access SharePoint sites that use SAML authentication. I described in a different post how to change the compat.browser file to essentially change the behavior when entering a SAML site so that it treats a mobile browser as a regular desktop browser (http://blogs.technet.com/b/speschka/archive/2010/11/21/some-windows-phone-7-and-sharepoint-2010-tips.aspx). That at least lets you authenticate with the site, and then you can use the normal browser views of the site or you can manually navigate to the mobile pages.
When SP1 and June CU came out however, the method of modifying the compat.browser file to allow authentication quit working. Since that time a number of folks have looked at this and for now there is a new work-around that will provide the same behavior as before. To do this, you need to modify the web.config file for each web application that you intend to use your mobile devices on. To get this behavior add the following snippet in the system.web section of the web.config of your Web Application:
Version=184.108.40.206, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
Making this change should allow most mobile devices to access a SAML secured site. It does not, however, enable the Office Hub application in Windows Phone 7 to work with the site. If or when the story changes on mobile support I'll update the blog with another post.