One of the nifty new features available in Silvering 3 is the Local Connection API. This makes it extremely easy to communicate between two different Silverlight applications. Granted, you could communicate between Silverlight instances before, but you had to use Javascript as a go-between. Now, it is much, much simpler, and as an added bonus, Silverlight apps can communicate from different browser pages! An app loaded in one browser tab can (with the right permissions) communicate to one on a different tab. Pretty cool, eh?