Thus far the best C++ UI libraries I've run into are Qt, GTK, and wxWidgets; Are there existing libraries similar to jGoodies or 'better'. I am interested in mature (yet simple) technologies.
QT is about as good as it gets AFAIK.
Binding a Java toolkit to C++ is a rather convoluted idea since in C++ you usually have a direct interface to the OS widgets. going full circle through Java is guaranteed to have uglier results.