Depending on the type of site you are running in WordPress, you will want to setup the initial user registration role correctly.  When you initially install and configure WordPress it creates the default Administrator Account.  From here you will want to create additional users with various roles, and assign the new user registration with a default role.

High level these are the different user roles in WordPress 2.x-3.0:

• Administrator – Somebody who has access to all the administration features.
• Editor – Somebody who can publish and manage posts and pages as well as manage other users’ posts.
• Author – Somebody who can publish and manage their own posts.
• Contributor – Somebody who can write and manage their posts but not publish them.
• Subscriber – Somebody who can only manage their profile.

For Example, if you are running a cooking Recipe Site/Blog you would want to make the default user registration role a Contributor.  This way other people can come to your site, add recipes as Posts, and you or another Editor can approve  them. 

For more on WordPress Roles and Actions, visit WordPress.org, or get started with your own WordPress Hosting Plan.