I find useful
groups.google.com/group/comp.lang.prolog/topics
cs.cmu.edu/afs/cs/project/ai-repository/ai/areas/
google.com/Top/Computers/Programming/Languages/Prolog/Implementations/
allisons.org/ll/Logic/Prolog/Examples/
prolog.info/
Maybe there are other useful links? Please share it :-)