A paper that is both a text and an executable program that plays music. Made by Tom 7 in his custom C compiler. More info here.
Source code for converting text into ASCII stereograms. The source code itself is a also stereogram (cross your eyes to get 3D-effect).
Hermannn2 by Immanuel Hermann, 2001.
Demonstrations of Most Complex ASCII Fluid by Yusuke Endoh 2012. The top one is a code calligram, where the code spells out Fluid and then turns itself fluid. Got an honorary mention in the Obfuscated C Code Competition.