I need to make a nicer-looking version of this image:

Is there some program that generates these graphs? Or are they done by hand in something like Visio?
(I'm on Mac OS X, and I have access to Windows if needed)
I need to make a nicer-looking version of this image:

Is there some program that generates these graphs? Or are they done by hand in something like Visio?
(I'm on Mac OS X, and I have access to Windows if needed)
On
I've found Gliffy to be a great method of doing this, and it has the advantage of being totally web based--nothing to install or screw up across operating systems.
On
The igraph library for R allows you to plot graphs. Combined with tikzDevice, it can also produce LaTeX output of the plots.
Here's an example:

The graph itself was produced using the R code
g <- graph.empty() + vertices(letters[1:3])
g <- add.edges(g,c(1,2,2,3,3,1,2,2))
g <- as.undirected(g)
and was plotted to a LaTeX file using the R code
tikz("~/Dropbox/Thesis/Thoughts/temp.tex",standAlone=FALSE,width=4,height=4)
plot(g,layout=layout.fruchterman.reingold,vertex.size=30,edge.width=3,edge.color="black")
dev.off()
Try Graphviz.