BuGLe: A tool for debugging applications that use OpenGL.
FRAPS: FPS (Frames Per Second), video capture, and screen capture for DirectX & OpenGL applications
gDEBugger - OpenGL debugger: Commercial OpenGL debugger
NVIDIA: OpenGL related tools for developers.
OpenGL Switcher: A small Windows utility for switching OpenGL driver DLLs back and forth.
The SphereXP: 3D desktop replacement for Microsoft Windows XP