For those who may be wondering why bother with another graphing tool, when Gramps already produces many nice charts: another benefit of using a graph viewing program is that it can give you a sense of the scope of your research, in a way that you don’t get just by looking at trees containing only people and families.
In the attached screenshot (which I hope you can enlarge to view), notice the disconnected sets of nodes over on the right side. In this case, they include not only persons and families, but also events and places, that are not connected to the mass of data on the left. (Again, for this example I used the Gramps “example” database.)
Tools such as yEd (which I used here) allow to vary the shape, size, color etc. of nodes and edges based on attributes in the data. So, for example, you could color the person nodes green, the family nodes red, etc. I have not done that here.
Another feature of such tools is to find hierarchies or clusters within the data. And it’s worth repeating that the nodes and edges can represent whatever you choose to put in the input file – sources, citations, anything.