I don't know why I neglected to mention this site when I did my "Top Ten Web Links" a month or so ago... I use this site all the time!
I'm never sure what a PG rating on a movie means anymore. Some PG movies have been shockingly "nearly-PG-13" in my book. And many PG-13 movies should have been rated R by my standards! I don't take the kids to see anything that isn't rated G before checking it out first anymore...
Before I go see just about any movie (with or without kids) I look it up on this site:
The site has a rating system (on a scale of 1 to 10) to give you an idea of how much sex & nudity, violence & gore, and profanity there is in the movie. It even breaks it down and tells you the details of why the reviewers came to that particular rating. As a parent and an individual, you can make an educated decision whether you want to view a particular film or not.
For instance, there is one movie in the theaters right now (I won't mention names) that looked absolutely hilarious on the previews and has some of my favorite actors in it. It was rated PG-13 so I thought it might be okay. After looking it up, however, and realizing that it had a rating on Kids-in -Mind of 7.3.4 (and after reading the detailed review of the sex & nudity rating of 7), I decided I'd rather not see it. We decided to see something else instead.
Another site with family-friendly movie reviews is Parent Previews. While the information on Parent Previews is not as detailed as Kids-in-Mind, it still offers reviews that can help you determine whether a movie is one you want to see or not.
"A Stanford University psychologist, Albert Bandura and a number of associates have amassed a great deal of evidence that has repeatedly and powerfully shown how models on TV and on the theater screen can teach new behavior patterns and influence or even change opinions, attitudes, and values." source
I choose not to give that kind of power and influence on my children and family to Hollywood. No, thanks!