Great question! Because of the infiltration of the occult and New Age into so much of our culture and media these days, we receive a substantial number of requests for advice on this subject.
Here are a few of the places I go to when looking for solid advice on books and other media forms from a Christian point-of-view.
Probably the best site I have found for researching books from a Christian perspective is found on the Focus on the Family website.
For those looking for reviews of books for children under the age of 18, check out Catholic Sense Media.
Christian Children's Book Review is another good site for reviews.
Reedeemed Reader is worth checking out for books for all ages.
This site reviews movies, TV and music from a Catholic perspective:
For those who are worried about books found in school libraries today, this site, which is operated by concerned parents, offers a large data base of book synopses that can spare busy parents the time it takes to read through a book. It also has lots of practical advice from other parents about what to do if you find an inappropriate book in your child's school.
For music, movies, TV, and video game reviews from a Christian perspective, visit Plugged In, a ministry of Focus on the Family.
TV & Movie reviews - the best publication around is Dr. Ted Baehr's Movieguide .
I also regularly visit the Parents Television Council site for TV viewing guides, reviews and other media research reports that are generated by this exceptional organization.