EzBasic - A C++ based library, that can be used to make programs using functions as in VB. The library has 25 classes ranging from GUI, Threads, String, Active-X etc.
Scripting Tcl interface to Qt multiplatform library
The GLAM toolkit is an OpenGL-based cross platform user interface toolkit for creating 2D or 3D user interfaces. Its main purpose is to provide the underlying framework for a user interface, leaving the visual look and feel to the developer.