1. Open Agent Engine
    Open Agent Engine is an object oriented graphics framework based on classes representing OpenGL 2.0 windows (opaque and transparent), and OpenGL views with methods to handle rendering, animation, mouse input, keyboard events, gamePad input, texture management, and shader manipulation
  2. OpenGL
    Interfaces and implementations of the OpenGL 3d graphics library
  3. opengl-extensions
    Extends cl-sdl to add bindings to opengl versions 1.3-2.0
  4. opengl-text
    opengl-text is a library for loading and displaying TrueType fonts as texture maps in OpenGL
  5. OpenMCL
    OpenMCL is called Clozure Common Lisp (CCL) now
  6. OpenMusic
    OpenMusic is a visual programming language based on Common Lisp and CLOS
  7. ops5
    OPS5 is a rule-based or production system computer language, notable as the first such language to be used in a successful expert system [...].
  8. opticl
    An image processing library for Common Lisp
  9. optima
    [deprecated by trivia, see link below] A pattern matching library
  10. Option-9
    A shoot-'em-up game written in Common Lisp