Have you ever had to model a decision process or flow diagram with Visio (or non-Windows equivalent) and wanted to automate the process cause it was a waste of your time drawing every arrow?
I've recently discovered Graphviz which caters for my geeky inclinations of 'just draw it' to see the structure, I don't care if the thing is perfect. I'm currently trying to map a decision process and the decision that are dependent on external data and influences. Now in a standard tool I'd have to redo the arrows carefully for every change, but not Graphviz. I can just add another connection line and regenerate. Cool beans :)
The nicest part for me is the specification of nodes, connections and labels, it makes sense! (In a CS way)
node [shape=box, color=green, style=filled]; Pesticide; Hectares; Fertiliser; CropType; Cultivar; PlantingDate; Livestock; SoilPrep; Hedging;