Greetings,
Article Manager allows for hundreds of login accounts with up to 4 different access levels: Writers, Trusted Writers, Editors or Administrators. Writers can create articles and submit them for review. Trusted writers can create articles and submit them to be posted live on the site. Editors can review articles, add appropriate changes to the articles, and approve for them to go live. Administrators can manage the entire program by creating new user accounts, approving articles, orwriting their own.
Individual writers and editors can be granted access to all categories or specific categories only.
"Article Manager", price $399, can be found:
http://www.interactivetools.com/products/articlemanager/faq.html#6
(REMOVE SPACES if they snuck into the pasted URL)
Good luck,
Maxwell