This is a shameless plug that may be of interest to GLUT users.
LibNUI is a GUI toolkit compatible and a multiplatform framework that does all it graphic rendering with OpenGL and/or Direct3D.
A few days ago, we have added a very simple way to use the toolkit inside a GLUT application. It has only been tested on WinXX and MacOSX but it will be really easy to add to the Linux backend.
So if you desperately look for a way to include a nice UI in your GLUT app, you can have a look at some very basic sample code here:
Or more generally check out the main website: http://libnui.net or the development site: http://redmine.libnui.net/wiki/libnui
Oh, and the lib is available under two licences: GPL and commercial.
Let us know what you think!