Once in a while, I find really great things available in SharePoint object model. The other day I was working on custom SharePoint security component and discovered quite few usefull properties in SPWeb.Groups -> SPGroup. In my case I had to determine whether current user belongs to a group and this is exactly a property of the SPGroup object ContainsCurrentUser. Another usefull one CanCurrentUserManageGroup.
Above properties can be used in a custom navigation control or any view logic that toggles the state depending on whether current user is in group that has access to the data.
