smallpt is a global illumination renderer. It is 99 lines of C++, is open source, and renders the above scene using unbiased Monte Carlo path tracing - http://www.kevinbeason.com/smallpt/

Code review Doom - http://fabiensanglard.net/doomIphone/doomClassicRenderer.php

Story of Game development on NES - http://games.greggman.com/game/programming_m_c__kids/

Fast Approximate Anti-Aliasing (FXAA) - http://www.codinghorror.com/blog/2011/12/fast-approximate-anti-aliasing-fxaa.html

Free book - http://www.gabrielgambetta.com/computer-graphics-from-scratch/introduction.html