Online Compiler Ressources

Compiler Construction by Niklaus Wirth, includes an Oberon-0 compiler.
The P4 Compiler and Interpreter by Steven Pemberton and Martin Daniels. Decribes the compiler which made Pascal popular.
Parsing Techniques - A Practical Guide by Dick Grune and Ceriel J.H. Jacobs. Less theorical and more recent than the first volume of the Theory of Parsing, Translation and Compiling by Aho and Ullman.