Another suggestion regarding Dee Roytenberg's request for
... a good text on the subject [Applications of (higher) category theory to computer science]? ...
in addition to
Category Theory applied to Computation and Control, ... 1974, ... :
there's also perhaps David Spivak's very 21st century Category Theory for the Sciences, ISBN 978-0-262-02813-4, MIT Press, 2014. Very little actual category theory, apart from definitions, examples and illustrations, but it's exactly those examples and illustrations (taken from computer science, from sociology, from physics, from biology, from operations research, etc.) that may be what the OP is seeking. Be aware that, in this book's presentation, Yoneda's Lemma finally turns up somewhat past page 400 (of 486 pp. total), and, for its proof (which I guess lies beyond the scope of Spivak's book), the reader is referred to Mac Lane's Categories for the Working Mathematician :-) . Cheers, -- Fred [For admin and other information see: http://www.mta.ca/~cat-dist/ ]