Here’s how to Install WordPress 3 with the New Multi-Site Capabilities — Even if you Already Have a Website in your Hosting Account. [Updated, works on WordPress 4 through at least WP 4.5)
WordPress multi-site features let you very easily create blogs (now officially called “sites”).
You can now have multiple blogs in WordPress with much less administration of WordPress updates, plug-in updates and settings, theme updates, etc. Multiple blogs, for each domain you are hosting, can be managed by a single installation of WordPress. (more…)