A Prolog Compendium
by Marc Bezem.
This is an excellent conceptual overview of Prolog
suitable for the logic programming component of a
Principles of Programming Languages course.
YAProlog, :- Yet Another Prolog, http://www.dcc.fc.up.pt/~vsc/Yap/
Anne Ogborn, Real World Programming in SWI-Prolog, http://www.pathwayslms.com/swipltuts/index.html