Run time rendering of XAML code

Most WPF programmers know the mythological XAMLPad tool, but it's supplied without source code (although the EditingExaminer sample should be something close to it).
You can also find Kaxaml, XamlHack, and now you can get Petzold's "XAML Cruncher", with source code.
It should be a nice tutorial on run-time rendering of XAML code.