David, the author of the upcoming Pitchers Duel baseball game has made a nice little module for pygame and opengl.
It allows you to use some of the GUI libraries with PGU. In the examples, it uses the excellent PGU, and Ocemp libraries.
However I think the general method can be applied to other GUIs fairly easily. It does the drawing on off screen surfaces, updating opengl textures as needed.
It even has a zooming demo... where the gui zooms. I like things that zoom.