Originally Posted by harvey

yes, it's called WordPress

Just read this to get a grasp at the ALREADY INSTALLED user level capabilities

Now, if you're serious about this and want to avoid trouble, I'd recommend you to use multiuser and give a blog space to each member so they can do whatever they want with minimum intervention on your side. It will take you a few mins/hours depending on your skills level and what you want to do, but it's the smartest way to do what you want