A little side project I built (Web + Chrome browser extension). The extension creates a way to comment on all web pages, highlight text, or you can simply bookmark. All public posts are searchable and you get your own shareable profile page of publicly "liked" links.
CrowdPlace - a social site built on Neo4j
A different type of social site in that depending on the context (what channel you are in) the data input and output can be different. So a post is a little more contextual and structured. It also allows you to follow RSS feeds in just the same way you would follow people, creating a newsfeed integrated with the social feed.