Someone made me aware of Gephi today. Gephi is a free, open source, and pretty powerful graph/network visualization tool. You can download it for free. (NOTE that there is generally an error when you install Gephi on Windows; the error is simple to fix, watch this video)
There are a bunch of tutorials.
To get started, I recommend these two videos:
If you want even more, the person that created the two videos above created this video play list.
Gephi supports multiple formats including CSV. While CSV is not really a graph, you can express nodes and edges in the CSV format and then import them into Gephi. Two other graph formats are supported: Graph Modeling Language (GML) and Graph Exchange XML Format (GEXF).
Here are some sample data sets that you can use.
If you don't understand graphs, I recommend this Introduction to Graphs (Part 1) tutorial.
Gephi supports a lot of different formats. While Gephi does not support XBRL yet (maybe it will some day); you can convert XBRL presentation, XBRL calculation, and XBRL definition relations into one of the supported formats extremely easily.
Here is a graph of common concepts used to report current assets using US GAAP. You can turn that into this where the size, color, and width of the nodes and edges have meaning.