For some time now I was experimenting with the SharePoint Blog template. Did you notice, how when viewing the post under permalink you also have the related comments?
Being curious I continued to research, found that there are no web part connections. But when editing the web part current view, I've discovered a beautiful thing!
Now there is besides [Today] and [Me] that you can use for filter value, also [ID]. Perfect for making display forms and related contents. So now in new SharePoint you can filter also by ID passed in URL parameter.
Let me run that through again: First when setting up a list view, set up the filter with the following value: ID is equal to [ID]
When the list view is set, now you can use the ID parameter in the listview:
And the list view is going to display the item with that ID.