Diaspora is a new social networking website being developed which intends to provide its users with control over their information, and this is what makes it stand out from various other social networking sites. Diaspora will not expose your information to advertisers or other websites, and you retain full ownership of any photos, friends, or information you put on the web site.
As it is still under development, the service is not yet publicly available. Following the link at the top of this post will take you to a page which enables you to request an invite. There is no guarantee that you will receive one in a short period of time, but it's worth requesting one as early as possible.