The font in Concrete Mathematics, interestingly enough, is a reparameterized version of Computer Modern. I'd have to look at the MF sources, but if I recall correctly, it doesn't have any changes to the actual character programs. The "math italic" is the Euler typeface designed by Hermann Zapf. While this was implemented in Metafont, it is not really a "meta" font. Instead, the grad students who worked on this (under the direction of Chuck Bigelow and Kris Holmes, IIRC) instead created MF outlines for each size independently. There is no shared code for different sizes or even for common aspects of the characters in the font.