Over at Epiphenom, Tom Rees has a nice ‘Research Blogging’ style article (Efficacy of prayer questioned) about a paper by Francis Galton dating back a few years now – doing the review as if it were of a contemporary paper.
Bottom line: no statistical evidence for efficacy (but it might make people feel good).
Galton, F (1872). Statistical Inquiries into the Efficacy of Prayer. Fortnightly Review , 12, 125-135