The Bacta Review   A New Kind of Science
For a good account of the actual mechanisms of biological pattern formation, as they are being revealed by molecular developmental biology, see John Gerhart and Marc Kirschner, Cells, Embryos and Evolution: Toward a Cellular and Developmental Understanding of Phenotypic Variation and Evolutionary Adaptability (Oxford: Blackwell Scientific, 1997). This book provides an excellent discussion of the interactions between genetic control, self-organization, evolutionary forces and functional adpatations in development. (There is a nice review by Danny Yee.) --- The failure of experiment to turn up any biological system working according to Turing's principles was remarked on by the late, great John Maynard Smith in his review of Depew and Weber's Darwinism Evolving (in the New York Review of Books, vol. 42, no. 4, 2 March 1995); my search of the subsequent literature doesn't indicate that the situation has changed.

Update, 4 March 2012: See the update at the end of the main post.