As there's been some discussion about what's in some films recently (Fred Claus, Holiday in Handcuffs to name but two), I thought people might find these sites useful:
They're two sites from the British Board of Film Classication (the people who decide what films get what rating in the UK).
The top site's the main one and the bottom one is for parents and has lots of input from parents.
Both sites contain lots of useful info about what's in films. The UK ratings are quite similar to the US ones (but it won't have all made for tv US movies as it's based in the UK!).
So a demo search for fred claus gives you:
I hope that helps! I'm not a parent myself - but for even me it's nice to know what you're letting yourself in for!