The course notes from siggraph about advanced opengl techniques - very useful.
A summary of many non-photorealistic rendering techniques.
Some free meshes can be found at 3D cafe - there are others too, try google for more.Mesh converter - e.g. 3DS to "C" -there are others too, try google for more.
GLUI - a glut based user interface library that includes such things as buttons, checkboxes, etc.
You might also consider investigating Qt for an alternative more advanced gui builder
One way to include sounds in your final project - there are others, feel free to use google to find others.