StatusNet
Formerly known as Laconica StatusNet is a Free and Open Source microblogging platform which helps people in a community, company or group to exchange short (140 character) messages over the Web. Users can choose which people to "follow" and receive only their friends' or colleagues' status messages. It provides a similar service to sites like Twitter, Jaiku, and Plurk.

Dolphin Hosting
Dolphin Smart Community Builder is a universal, free, open source software that allows you to build any kind of online community. With a huge variety of features & options, you can quickly launch your very unique and successful website. Dolphin is a professional, full featured, secure community software that allows you to start a unique on-line community web site. Dolphin-Smart Community Builder is a simple-to-manage and easy-to-customize, PHP, MySQL, XHTML based community script. It offers features like: Forums, Photos, Video, Music, Blogs, Polls, Events, Groups, Chat, Messenger, Boards, Design Templates, and a lot more.

BuddyPress
BuddyPress is a bundled collection of plugins and themes for creating a social network service around an installation of the popular open source blog engine WordPress MU. By releasing the BuddyPress pack, WordPress stepped into the social network field with almost unmet functionality and features.
BuddyPress is a set of WordPress plugins and themes which extend the multi user version of WordPress with many social network features such as extended user profiles, private messaging, friends lists and groups as well as user wall (wire). BuddyPress contains all the features you would expect from WordPress but emphasize on the members social interaction. It is free and is intended to provide anyone with a working social network "out of the box".
Although not as elaborate as Facebook, Bebo or MySpace, BuddyPress is designed for small-scale networks around niche ideas/interests.

eMeeting
eMeeting is an advance community software providing one of the largest set of features on the market. Usign the eMeeting software you will be able to easily create your dating or community website with detailed member profile support. Furthermore, eMeeting supports events callendar, mobile messaging alerts, visitors location map and many more. The admin area of eMeeting is powered by advance SEO tools, affiliate tracking, multiply languages support, theme editor, content manager and all standard features which will need to fully manage your community or dating website. eMeeting dating software is the perfect choice for business owner, website design agencies or individuals looking to create a dating website for themselves or a client. Packaged full of advanced industry standard features and functionality, eMeeting dating software is a feature rich, all-in-one solution for any profitable dating website business.

AbleDating
AbleDating is the only dating and community script in the world with AJAX, 3D Chat, and FLASH games! Powerful, fast and stable PHP/MySQL-based open-source dating community software with Protection against nulled versions usage. This community script will make your online dating business successful. It offers you Video Chat, VoIP Phone, Flash Chat, Flash Games, 3D Chat, Greeting Recording, Hot-or-Not, Forum, Blogs, Gallery, Video Gallery, Friends, and 100s of other superb features!
AbleDating is an advanced matchmaking, dating, personals script with complex customization options including custom membership upgrade packages, content management system, unlimited profiles per account, unlimited pictures, custom payment gateways, internal messaging, multiple admin tool scripts.

PhpFox
PhpFox is an advanced social networking application that offers you a long list of features. Some of them are: Video module, music, gallery, poll, forum quiz, event, instant messenger, etc. You can use PhpFox for personal or large projects.

Elgg
Elgg is an open source social networking platform. It offers blogging, networking, community, collecting of news using feeds aggregation and file sharing features. Everything can be shared among users with access controls and everything can be cataloged by tags as well.
Elgg powers all kinds of social environments - from education to business and sports such as rugby. If you are looking to create your own social application or want to build and run a site for your organisation, Elgg is a great choice as it provides the building blocks you will need.

eFriends
E-Friends is an online social networking software that allows you to start your own site just like Friendster and MySpace. The E-Friends software allows members to connect to people in their personal networks and community, creating a new online interactive resource that is based on a trusted network of friends and associates on the internet. Starting a MySpace clone has never been so simple with E-friends social networking script.
Members can use this abundant network to make friends, find their love ones, locate jobs, buy and sell stuff, locate a roommate, and accomplish much more with the help of groups and individuals who they know and share the same interests.