Most of the links below are relatively introductory, but they do serve as a quick refresher if it has been awhile since you have worked with Silverlight.
Though not all of the links are specific to SL4, I would recommend a path of RIA services in conjunction with ADO .Net Entity framework for your business apps as these new process flows simplify the project structure and are improvements upon their predecessors.
For quick “agile” development, Linq to SQL is still the way to go IMO, but ADO .Net is also great nonetheless.
– Walkthrough creating a silverlight business application (4.0 or later) and retrieve data using WCF service.
– Using ADO .Net Entity Model / Framework with Silverlight (4.0 or later)
– Silverlight custom data forms (3.0 or later)
– Basic Animation in Silverlight
– General Reference (all versions)
– Run Silverlight on Desktop (Out of Browser Application)