To start, choose either the
The OpenGL Reference Manual: The Bluebook.
The OpenGl Programming Guide: The Redbook.
More information and tutorials at OpenGL.org.
There is also an introductory page located at glXIntro.
The GLU tesselator has changed in version 1.2; here are some
notes on the new GLU tesselator
For more OpenGL information, I suggest starting at The OpenGL WWW Center.
You can also read the hypertext version of The OpenGL Graphics System: A Specification (Version 1.0). In this document all formulae are given as images, so they look much better than my ASCII art.