I was hoping to relase a new (and very late release) of AutoDia this weekend, but I having looked at Marcels code I can see some very obvious improvements at the design level (in my code, not his) and I would feel a fraud if I released a version that had all the work done by other people.
More importantly after mentioning charting and stuff on the Dia mailing list James DuPont pointed me at some peers of the Graphviz project and even a Graph/Chart XML schema.
VCG (Visualiser of Compiler Graphs) - offers auto-layout and folding and stuff, very very cool but I haven't had a chance to play yet.
Graphotron
'Graphotron is a simple XML language for drawing graphs with XPath' apparently.
as a side note - I have managed to get a simple Traffic Analysis Graph working with real web logs at work. Its not very pretty but I am certain that it will be very helpful - even more so if I combined it and a couple of other charts into a database backend to provide interrogation tools.
