Here's one that I found really good.
http://culturalpolicy.uchicago.edu/conf200...s/freedman.html
I have a whole list of references, but many of them are DOJ links and whatnot to statistics, as well as references to TV violence (since I drew a parallel to it, since the media does as well). I can give you a larger list, some of which is good/bad for video game violence defense.
For the most part, the non "fire and brimstone" studies point out inconsistencies with the other studies (the one I linked to you talks about a study that compared Myst to Wolfenstein3D, stating that the games are functionally identical in every aspect except for violence/aggression). It's an evaluation of the research on violent video games.
If you want more links I can give them to you, but you'll have to do a bit more sifting through them (which I would recommend anyways).