I haven’t tried all this software yet. So I can’t endorse it exactly… But when I do give it a shot I’ll write a review. I hope to add more to this list as I find them.
OneSocialWeb The purpose of onesocialweb is to enable free, open, and decentralized social applications on the web. Its protocol can be used to turn any XMPP server into a full fledged social network, participating in the onesocialweb federation. The suite of extensions covers all the usual social networking use cases such as user profiles, relationships, activity streams and third party applications. In addition, it provides support for fine grained access control, realtime notification and collaboration.
Opera Unite Opera Unite is a new technology platform allowing you to share content directly with friends, without having to upload anything to a Web site. You can stream music, show photo galleries, share files and folders, or even host your own Web pages directly from your browser.
Diaspora (Due in October 2010) the privacy aware, personally controlled, do-it-all distributed open source social network
Pligg is an open source CMS (Content Management System) that you can download and use for free. Pligg CMS provides social networking software that encourages visitors to register on your website so that they can submit content and connect with other users. Our software creates websites where stories are created and voted on by members, not website editors. Use Pligg content management system to start your own social networking community in minutes.