I am really enjoying the Jms Multisite system from http://www.jms2win.com/index.php.
I have a client that uses the system to manage several subsites that are contained within a central site system. They will be administrating all the sites from the main admin panel. each site will contain a subset of products and articles, all of which are handled via the shared database. The only thing that will be done in the site-specific-admin-panel areas will be the menus for each site.
Because of Jms Multisites, this project has not been a nightmare! I love it. And Edwin, the developer, is very good with support. He will answer questions quickly on the forum.
It's a big project, with many many details, but I think we are finally wrapping it up, and I'm excited about rolling out in a few weeks.
