Port for drawing directed graphs?

[John Almberg]

I am working on some software that must, as it's final output,  
produce a printout of a directed graph... nodes, connected by  
directed links.

The printout could be generated by a postscript file, jpg, whatever.

Does anyone know of a utility (in ports?) that can take a data set  
(for example, a two dimensional array that defines the nodes and the  
links between them), and produce a printable graph?

Any help much appreciated.

-- John