I am creating sort of a \"Navigation panel\" (which is actually an ItemControl) for SL and using Regions to allow each module to add his link to the panel.
Problem i
This is not built into Prism regions, however it's easily implementable.
Damian Schenkelman has posted an extension method he created for adding a region to an index that seems to work pretty well. http://blogs.southworks.net/dschenkelman/2009/03/14/how-to-add-a-view-to-a-region-in-a-particular-index-with-prism-v2/
Hope this helps.