Edward Fredkin's papers exploring the idea of a world where all quantities in nature are finite and discrete, with a chapter on cellular automata. http://digitalphilosophy.org/
General Cellular Automata Java applet running over 200 rules from 12 CA families, equipped with a big library of patterns. By Mirek Wojtowicz. http://www.mirekw.com/ca/mjcell/mjcell.html
A repository with cellular automata related papers, lectures and software concentrating on Rule 110 by Harold V. McIntosh. http://delta.cs.cinvestav.mx/~mcintosh/
A site devoted to the Edward Fredkin's idea that our entire Universe can be represented as a computer program. FAQ, relevant articles, cellular automata pictures, movies, VRML models and programs. http://digitalphysics.org