Here's a little website I encountered just now: "what they play".
It is a site oriented at parents with information on contemporary video games. Warning them of extreme content, guiding them to a proper choice for a game for their children, as well as allowing the general public to write their own reviews aimed at informing parents.
I also spotted a nifty piece on how some children intend to circumvent the ratings of some games, and get a restricted game anyway. Answeres ran,ged from older friends or siblings (like alcohol), to a "dealing" doorman. Interesting stuff to say the least.
With the recent GTA:IV bonanza, I tought it might be interesting.
While I personally do not believe there is a link between violent video games and (increased) violent behavior, I will leave such judgement up to you when dealing with your children.