There are many websites with useful information regarding this topic, which maintain updated information about new issues which appear in the news, and also talk about possible solutions and ways to limit the negative impacts of media on children.
One great website is Common Sense, (https://www.commonsensemedia.org/), which was created mainly to help parents with analysing if movies, and other types of media including apps, TV channels and other, are suitable for children and at what ages. It also provides helpful information for parents about their possible concerns with media including cyberbullying, children’s marketing, violence and sex exposure and other possible threats.
A website, which not only provides information for parents about the negative effects of media on children but asks parents and others to act in order to change what children are exposed to, is the Campaign for a Commercial-Free Childhood website (http://www.commercialfreechildhood.org/). It provides helpful advice to parents of how to make children less dependent on all kinds of technology and help them separate themselves from the ever-present media influence.
Although more broadly, the American Academy of Paediatrics also provides information about the influence of media on children by providing an academic analysis of the problem. Although they focus on other issues surrounding children and their development, here is the direct link to where they provide information about media: https://www.aap.org/en-us/advocacy-and-policy/aap-health-initiative1s/Pages/Media-and-Children.aspx.
Another very useful website is the one of Net Family News (http://www.netfamilynews.org/). The website was founded by an experienced journalist Anne Collier and the whole site is based heavily on news articles and blog posts. Through this approach, it provides parents with information which they can read in an easily understandable way, which is well structured and also coherent. Most of these articles are written by Anne herself, which adds familiarity to the writing and makes the articles relatable.