2 Portals or other rich resources
Utrecht University's Attribute Grammar System tools include also an attribute grammar compiler, UUAGC. The concept of attribute grammar was used in their Essential Haskell Compiler project, which gives us not only a working programming language, but also a good didactical material about using attribute grammars, e.g. in writing compilers.
Albeits these materials are self-contained, they reveal that the theory of attribute grammars is related to other concepts (circular programming, catamorphism).