Coherent GT - Fast user interface runtime for PC and Consoles
Qt - Powerful, flexible and easy to use, Qt will help you not only meet your tight deadline, but also reduce the maintainable code by an astonishing percentage.
Sciter - Embeddable HTML/CSS/script engine
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Ultralight - Fast, light HTML UI solution for C++ apps
Avalonia - A multi-platform .NET UI framework