opengl.org: Selection and Picking and Feedback Mode
opengl.org: Selection FAQ
stackoverflow: OpenGL GL_SELECT or manual collision detection?
stackoverflow: glReadPixels() really slow, better solution to get OpenGL coordinates from mouse position?
The Game Programming Wiki
Delphi GL Wiki
lighthouse3d.com
OpenTK Selection/Picking
OpenTK GL_SELECT Performance
glprogramming.com
Picking with SDL and glReadPixles (BASIC-Programming)