MSBLayout is a layout manager for Java AWT and Swing that combines the nested-boxes approach of BoxLayout with flexible constraints as used by GridBagLayout. A concise API with good defaults minimizes the code required to get the layout you want. MSBLayout makes it easy to align and justify components and to synchronize their sizes. Gaps between components can be inserted automatically. Optimized resizing behaviour keeps your dialogs looking good when displayed larger or smaller than their preferred sizes. The API is also well suited for constructing layouts dynamically at run-time.
The Two-Layered GUI Toolkit is a library of GUI helper classes which is designed in a way to simplify development of separate interchangeable front-ends. For every supported dialog box type, there is a settings class (independent from a GUI toolkit) whose options can be used by one of the implementations for a specific GUI toolkit (bindings for Gtk#, WPF, and WinForms are provided, but custom ones can be added). That is, the dialog definition can be prepared by the application's core component and passed to the front-end, which uses it to instantiate the dialog box using whatever GUI toolkit it likes.