Last we heard Silverlight Mobile has missed targets for inclusion initial releases of Windows Mobile 6.5, but that does not mean development is not going on apace.
This video below shows a Silverlight application being embedded as a today screen plug-in.
Silverlight Mobile may end up being more important as a dynamic presentation layer on Windows Mobile than on the desktop, so hopefully the software will be delivered sooner rather than later.
Read more at the MSDN blog here.
Thanks Craig S for the tip.