Joe already blogged about the Site Studio 10gR4 samples and viewlets. The viewlets show how to do key Site Studio tasks, and the samples provide some Site Studio 10gR4 "artifacts" (element definitions, region definitions and templates, etc.) to get started with.
Along with the artifact samples is a new Site Studio Samples site designed to showcase them. This site isn't a traditional sample site. Instead, it presents the "sample" Site Studio objects in a self-documenting way. It's built with Site Studio, so it's sort of like an object browser built with the objects it is browsing.
Leaving aside the mind-bending aspects of it, here's what the sample site looks like. In this screen shot, we've navigated through a region definition, and are now looking at the templates that "know" how to format content authored to that region definition. Note the dependency documentation in the right column.
All the other sample Site Studio objects - page templates, element definitions, region definitions, and subtemplates - are presented in a similar manner and can be accessed using the vertical navigation on the left. The site comes as an archive, and can be loaded into any UCM instance with Site Studio 10gR4 enabled. Tell us what you think about this approach - both the samples themselves, and the site to view them in.