drawing graphs with large number of nodes/edges


I'm trying to draw a graph of how methods/functions of a program link to each other.
I've succeeded in creating a .dot-file for this.
The problem now is, is that the output of dot -Tsvg is somewhat unreadable: everything is clumped together and mostly horizontally. How can I get dot to spread things out a bit more?
I tried adding weights but that did not help.

see: http://vps001.vanheusden.com/~folkert/testout.dot and http://vps001.vanheusden.com/~folkert/testout2.dot