BOND (building object network databases) is database development framework for rapidly creating applications. It creates live forms for the Web with AJAX and desktop applications using GTK. Using XML to define widget layouts, it drives the live forms to which SQL statements and methods can be attached.
Faith is a cross-platform C++ graphical application toolkit. It runs natively on Linux/Unix (Xlib) and Windows. It has an API strongly inspired by Qt's and has many features that are expected from a modern toolkit, including a variety of common "widgets", an aesthetically pleasing appearance, and the many critical non-portable components such as anti-aliasing and sockets.
gtkmm (previously known as Gtk--) is a C++ interface for the popular GUI library GTK+. It provides a convenient interface for C++ programmers to create graphical user interfaces with GTK+'s framework. Highlights include typesafe callbacks, widgets which are extensible by inheritance, and many classes that can be easily combined to quickly create complex user interfaces.
XGui is a multiplatform, multilanguage native widget set. This means you can write your code once in your favorite language (C, C++, or Python) and then compile it to run on Linux or Windows with the native look of the OS. XGui is developed keeping in mind the MVC pattern. Lists and Trees are just views of a model. Even styles which define how to show the model in every different view are separated. GUIs, models, and styles can be saved and loaded from XML files.