Hello Elgg! (A Social Networking Engine)

Elgg was voted best open source social networking platform in 2008.

Highlighed features
1. Powerful Data Model
Elgg provides a powerful data model making the creation of different entities simple, yet flexible.
2. Activity Streams
The granular activity stream API ensures your plugins can push the required content to your users.
3. Plugin API
Use Elgg's powerful plugin API to build and add your required features.
4. User Management
Elgg handles your user management and relationship requirements.
5. Access controls
All objects in Elgg can have an access control level applied making granular access permissions possible.
6. Web Services API
Expose functionality through the REST API by building a plugin and then either publish the API for other developers to build clients or provide your own.

License
Elgg is free to download and use. It is dual licensed under the terms of the GNU General Public License v2 as published by the Free Software Foundation and the MIT License.
Built-in Feature

• Avatar
• Dashboard
• Friends
• Groups
• Profile
• Widgets

Optional plugins

• Blogs
• Bookmarks
• File repository
• Message board
• Private messaging
• Pages
• Activity
• Microblogging

Ubuntu Linux Environment

1. Install Apache webserver: sudo apt-get install apache2
2. Install MySQL database server: sudo apt-get install mysql-server
3. Install PHP: sudo apt-get install php5 libapache2-mod-php5 php5-mysql
4. Install phpmyadmin: sudo apt-get install phpmyadmin
5. Turn on the Apache module rewrite: sudo a2enmod rewrite
6. Edit /etc/apache2/sites_available/default to enable .htaccess processing (set AllowOverride to All)
7. Restart Apache: sudo /etc/init.d/apache2 restart

Note for installation on a virtual host (e.g. Rackspace, Amazon EC2)

For installation to proceed successfully, modify the .htaccess file in the root, and uncomment:

Modily #RewriteBase / to RewriteBase /