Socialize your family tree
Genealogy application allowing you to invite other family members to contribute and comment. Upload family pictures, add life events.
In designing the architecture for a family tree site, we decied to use a graph database, and we picked Neo4j. This gave us great flexibility in designing relationships between people.
This was then integrated to a regular rails app with user authentication, so that the user logging in could be linked to a person on the chart, and the authorization for what they can see is then calculated using the graph database to limit the relationships they can view. For example, you can see a non blood related aunt, but not beyond the aunt.