Lighthouse3D GLSL Tutorial
http://www.lighthouse3d.com/tutorials/glsl-tutorial/
Modern OpenGL Programming
http://en.wikibooks.org/wiki/OpenGL_Programming#Modern_OpenGL
Modern OpenGL Step-by-Step
http://ogldev.atspace.co.uk/
Learning Modern 3D Graphics Programming
http://www.arcsynthesis.org/gltut/index.html
OpenGLBook.com
http://openglbook.com/
AmazingKing Modern OpenGL Tutorials
http://www.theamazingking.com/ogl.php