Geneology of Influence
This site describes itself as ‘a visualization of the connections between the most influential writers, artists, philosophers, scientists, and mathematicians of Western culture.'
Users can follow links between great thinkers and see how they have influenced each other. For example Newton can be traced to Emerson, Voltaire, Jefferson and Gödel. When you hover over their names you are given a brief biography of them.
There's also an accompanying blog which an excellent companion to the guide an provides a great introduction to thinkers you may not have come across before. It's also a great resource for quotes.