Hi,
Is there any software out there that handles the content management and administration of multiple websites? What I'd like is the following:

• Multiple website domains running off a single software install.
• Undate the core with a plugin/extension once, the plugin/extension is available to all websites.
• Website will be available as a sub-directory e.g. www.parentsite.com/sites/mysite (or mysite.parentsite.com) and also as a domain e.g. www.mysite.com

Thanks,
Bearaman