I had the need to start working with Glu.Nurbs curves and surfaces this week.
To get a handle on the structures and procedures involved, I created a simple OpenTK example for using Glu.NurbsCurves and Glu.NurbsSurfaces. It's built using the example framework and the SVN revision 1324 of OpenTK. The Curve and surface data is from a RedBook example, if this is a problem, I can change the data.
Please consider this as my first contribution to OpenTK.
[Edit] I started to add trimming curves to the surface and the parameter GLU_MAP1_TRIM_2 is missing from the MapTarget enum.
[Edit2] It looks like the GLU_MAP1_TRIM_2 is actually a NurbsTrim.Map1Trim2, the Glu.NurbsCurve does not have a signature that is compatible with a NurbsTrim. I have not figured out how to add the missing overload.
I have updated the drawing code to allow trimming and commented out the trimming operation, its in the rev1 zip file.