Dyndyn is a GTK+2 Engine, whos main feature is to draw Dynamic widgets. Each and every widget is drawn a bit differently, making your desktop slightly more interesting.
GtkGLExt is an OpenGL extension to GTK+. It provides additional GDK objects which support OpenGL rendering in GTK+, and GtkWidget API add-ons to make GTK+ widgets OpenGL-capable.
Strip Charts for GtkPlot provides a set of GTK widgets for creating
strip plots of numeric data. Horizontal 'strips' of data are
ganged; supports
multiple color-changing limit (alarm) lines,
multiple scrollable cursors (with callbacks).
libgtk3dcanvas is a Gtk set of widgets to build easily simple 3D scene render engines.
You can add items (balls, stick, polygone, ...) like on libgnomecanvas, and then, you can declare several camera (OpenGL, Direct3d...) to render it.
Gdkxft transparently adds anti-aliased font support to gtk+-1.2. Once
you have installed it, you can run any (well, nearly any) existing
gtk+ binary and see anti-aliased fonts in the gtk widgets. You don't
need to recompile gtk+ or your applications.