This will allow your child to keep a low profile at first, until you feel they are ready to talk to others online. Most newsreading software is designed to allow you to jump into a discussion and reply to messages. Note that once your child posts to a newsgroup, they are no longer an anonymous reader. Others reading the newsgroup will see their name and electronic mail address, and may send them email. Online, of course, the backyard is as big as the entire planet.
Most chat services allow for the naming of a chat room that corresponds to a particular topic.
Establish some guidelines early on with your child about whether they can chat with others, and what topics they can chat about. Overall, you should probably set similar guidelines for chatting as you give your child for talking to strangers. Suggest that they talk only to people their own age, and if someone pressures them to talk, teach them to simply leave that chat room or server. As a last, you can report them to the individuals running the chat system. Many allow users to customize their own virtual spaces.