From Joomla! Documentation
How Do I Download Joomla?
It is easy to download Joomla! Just go to joomla.org and click the download button.
What Some of Joomla's Features?
User Management - Joomla has a registration system that allows users to configure personal options.
Media Manager - The Media Manager is the tool for easily managing media files or folders and you can configure the MIME type settings to handle any type of file.
Language Manager - There is international support for many world languages and UTF-8 encoding.
Banner Management - It's easy to set up banners on your Web site using the Banner Manager, starting with creating a client profile. Contact Management - The Contact Manager helps your users to find the right person and their contact information. It also supports multiple contact forms going to specific individuals as well as groups.
Search - Helps navigate users to most popular search items and provides Joomla administrator with search statistics.
Web Link Management - Providing link resources for site users is simple and you can sort them into categories, even count every click.
Content Management - Joomla's simplified three-tiered system of articles makes organizing your content a snap.
Syndication and Newsfeed Management - With Joomla, it's easy to syndicate your site content, allowing your users to subscribe to new content in their favorite RSS reader. Menu Manager - The Menu Manager allows you to create as many menus and menu items as you need.
Template Management - Templates in Joomla are a powerful way to make your site look exactly the way you want and either use a single template for the entire site or a separate template for each site section.
Integrated Help System - Joomla has a built-in help section to assist users with finding what they need.
System Features - Speedy page loads are possible with page caching, granular-level module caching, and GZIP page compression.
Web Services - With Web services, you can use Remote Procedure Calls (via HTTP and XML).
All of the above with Powerful Extensibility.