There is Gephi, which is very capable, though I've also found it frustrating to work with, particularly for graph editing. Interface glitches, unresponsive elem

There is Gephi, which is very capable, though I've also found it frustrating to work with, particularly for graph editing. Interface glitches, unresponsive elements etc. quickly get in the way. Development seems to have stalled somewhat, so I'm not optimistic that this has improved.