Genealogy of Influence is a dataset of influence links between historic figures started in 2005. I added the data to the database project Freebase where others have added thousands of connections. Some applications that use the dataset are listed below. The data can be accessed on Freebase here.
Changes to the Freebase API have broken these apps, sorry.
Recent additions
License
Genealogy of Influence is licensed under a Creative Commons
Attribution-NonCommercial-ShareAlike 2.5 License.
Wikipedia content is under the GFDL
Older versions of the data
A large graph visualization of the dataset made with Graphviz: PDF
DOT file which contains the links
Touchgraph applet
created using Touchgraph
(xml data)
PDF of the hierarchical layout
created using yEd
(graphml data)