Drawing preteens as young as 6 or 7, sites like Club Penguin and Webkinz are forcing parents to decide at what age they are willing to let their children roam about and interact with friends online. They, along with schools, are having to teach earlier lessons on safety, etiquette and balance with offline activities.

Although these social-networking precursors for tweens tend to incorporate more safety measures than MySpace, Facebook and other sites geared toward teenagers and adults, experts warn that parents can't simply sign their kids on and leave them there, especially during the summer months when kids have more time to spend online.

Parents should also start addressing safety and online etiquette.