The excellent book "C Interfaces and Implementations: Techniques for Creating Reusable Software" by David Hanson as well as "A Retargetable C Compiler: Design a

The excellent book "C Interfaces and Implementations: Techniques for Creating Reusable Software" by David Hanson as well as "A Retargetable C Compiler: Design and Implementation" by the same author are both written in the literate programming style. I'd definitely say it's unpopular, but hardly goofy from a pedagogical point of view. C Interfaces and Implementations is such a beautiful book and the literate programming style really compliments it well.