Social sites and social features are incredibly huge on the web right now. While it seems like every feature exists, the right combination and branding may not be there for your community, club, organization, or company. There are growing options for software that will allow you to run your own community, no matter how large, and will provide tons of features to keep your users interested.
Choosing which features are important to a community helps in choosing the system that you will start with. Many times sharing of information and running conversations online is the focal point. User permissions are also a strong consideration as you will be hosting a site that allows users to upload their own content.
For years now, the forum has been the focus of web communities as it is expandable and allows you to enter nearly every type of content to be shared. It tracks user information and allows for a wide array of permissions to be set. Styling is very flexible and unlimited category and topic creation is possible. Most people hear the word "forum" and only think of text display, but now it's easy to add embedded videos with the click of a button, upload photos, graphics, and documents to be shared, and organize events. The familiarity of layout is also a strong point allowing you to retain users that might otherwise leave if they are required to learn a new system.
phpBB3 is the most widely used open source forum software on the web, and for good reason. phpBB3 has been consistent in their support and updates and being the most widely used also makes them the most widely tested on a day in and day out basis. Much of the phpBB3 system configuration is completely customizable to your needs and can be extended with a user blog feature allowing not only traditional categories and topics, but user specific pages so users can post their information as they wish.
Forum software is often overlooked because of a misunderstanding in everything that it includes. It's highly recommended to inquire about everything a forum can accomplish as it's far more capable in various areas than other softwares.
Content Management Systems have been adding community features and have come a long ways in the past couple of years. An up and coming player in this field is Anahita which runs on Joomla!. This is an open source software coupling and has gone through immense research on how online social mediums grow and the mathematical nature behind these communities. Anahita is very powerful and considered a full Social Engine.
A strong focus on efficient code and future use makes Anahita a very enticing choice. Discussion boards, groups, photo sharing, user relationships, and ease of use sit at the heart of this software. Also, the code is written in a manner to allow application development, so the feature list will grow exponentially just as other softwares and gadgets have increased their apps libraries.