SwiXML is Wolf Paulus’ XML User Interface languge (XUI or XUL) which uses the regularity of the Java Swing GUI libraries to allow very lightweight implementation: XML elements are used for JComponents, XML attributes are used for properties (e.g. <frame size="5"/> would be JFrame.setSize(5)), and there is provision for layout managers, ids, custom JComponents and so on. Substance is Kiril Grouchnikov’s Look and Feel library for Swing components, which allows various subtle and lurid modern effects: the latest release, version 5, has just come out. Kiril has also written a good series of articles, available at his blog, on what he has learned about running a successful responsive open source project.
How to build Python desktop applications on top of the Mozilla application architecture. This Strategy is used by many successful applications - Firefox, Thunderbird, Songbird, Miro, Komodo Edit.