I can't seem to find them anywhere... are they gone?
You can create two types of trim marks in Illy CS6.
For either, select all the objects you want within the trim marks. One type is available from the Object menu and creates a group of the marks based upon the bounding box and are offset just as the marks are when you create a PDF.
The second option is (again with the object(s) selected) is available from the effects menu. These are a live effect and change dimension as the art is resized. Using this option, Illy places marks around each and every object unless you group all the objects. Once ungrouped, the marks are removed. These marks are also aligned precisely on the objects' bounding box instead of being offset.