This article explains how gamma correction works and why is necessary. This article describes one possible algorithm for generating triangle strips from any random bunch of triangles. Metaballs are a powerful way of modeling smooth, organic shapes. This article takes a look at how metaballs work. I think real-time cartoon rendering would be just as cool, if not cooler.
Quaternions are a compact way of representing rotations.
This article discusses how quaternions work and why they are so popular. This article discusses three useful techniques to implement a selection system. OpenGL isn't necessarily just for 3D graphics, you know. The framebuffer consists of a lot more than just the color buffer. This article takes a look at the other buffers defined by the OpenGL specification, and examines how much video memory each of them would require.