When Silverlight 2 was released I wrote a short document comparing the classes in the Silverlight System.Globalization namespace with those of the .NET Framework's same namespace. Last year I updated it for Silverlight 3 and now I have done the same again for Silverlight 4. Before you get too excited, however, the System.Globalization classes and their methods and properties in Silverlight 4 have not changed since Silverlight 3. That is not to say that there aren't internationalization changes in Silverlight 4 (right-to-left support being a very welcome addition), just that the classes themselves have not changed (not even to include TextInfo.IsRightToLeft). You can download the document here.