Here's another picture from generated with PostGraph and displayed in QGIS. I generated 100 random points in the plane and connected all of them together. The red lines are the graph edges (shown with 95% transparency). The blue edges are from the minimum spanning tree. The size of the circles indicates the weighted betweenness centrality of the network (using distance-squared weights).
Brad McRae who is a rather sharp lad has been adapting circuit theory to model landscape connectivity. We have a new paper out this week in Ecology. Check it out. 
If your are unfortunate enough to use openoffice for documents, you will want to install the Microsoft core fonts in Ubuntu (provides eg Arial and Times New Roman). The easist way to do this is to install the "ubuntu-restricted-extras" package. That will also install a bunch of other things that are not free and so are not installed by default. If you only want the fonts, install "msttcorefonts."
Some pointers on installing packages are here.
