Looking for materials specifically targeting OpenGL 2.1

Why would you want to look at 2.1? That's really old stuff.

http://www.opengl.org/sdk/docs/man2/

Did you look at this stuff?

The reason is because I am looking to write a simple renderer that supports much older hardware before OGL 3 and 4, or preferably find one that already exists.

http://www.lighthouse3d.com/tutorials/glsl-tutorial/