Malte I have found pqa (
http://pqa.projects.postgresql.org/ ) VERY useful for providing log analysis with postgres. I haven't used it with pg8 - you may need to check that the following patch has been applied to the version you use for compatibility with pg8:
http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pqa/pqa/lib/pqa.rb.diff?r1=1.80&r2=1.81
