I was happy to see Barron's this week recognize (link here, sub required) a strong study of corporate charitable giving from NYU that won an Honorable Mention in this year's Moskowitz Prize competition.
This is one of those topics that raises all sorts of interesting questions, but where there has been virtually no empirical work (the only other decent study I'm aware of is Navarro's 1988 paper). One of the most important aspects of this paper is the work they did trying to sort out causality. Of course rich companies give money to charity - but do they derive a business benefit from doing so? Consistent with Orlitzky, they find the answer is 'yes'.
Does that flow through to stock prices? Don't know. More work is needed! But this team is to be commended for exploring this neglected but important area.