We have been working hard with the Zoo Component From Yootools (http://www.yootheme.com/zoo/) but one missing feature in the Related Items Element is the ability to select items in other applications.
For example in the Blog application we can't select a related item in the download Application or viceversa.
With this modification to the standard element "Related Items" you can do just that. We integrate this functionality independent of the main related items element so any update to Zoo will not affect the new element.
Extract the folder "apprelateditems" provided in the zip to the folder administrator\components\com_zoo\elements in your Joomla Folder and associate the Element with any Application and Layout.