You can use Aurora XAML Designer to create standalone WPF applications or custom libraries for reuse. The Aurora XAML Designer provides resource libraries of pre-built XAML components -- just select a component and add it to your design surface.
You can also access the Aurora XAML Designer Toolbox, which provides custom control components:
Aurora XAML Designer can also be used as a Visual Studio plug-in for WPF design-time support. In addition, the Aurora authoring engine is built as a WPF DockPanel that can either be dropped into a WPF application, or embedded in a WinForms application, providing XAML/WPF authoring support.
Try it out and let me know what you think, Lorin