WPF CodePlex toolkit, charting made easy...

Charting made easy: graph, pie, bars, points... 
Free, opensource, maintained.

"The WPF Toolkit is a collection of WPF features and components that are being made available outside of the normal .NET Framework ship cycle."

Sources

• Windows Presentation Foundation (WPF)

Guide: Drawing graph for free using GraphViz opensource lib.

• Install GraphViz... 

• file.dot

digraph G {
Yehiel -> Shlomi;
Aviva -> Shlomi;

David -> Rotem;
Ilana -> Rotem;

Shlomi -> Yeara;
Rotem -> Yeara;
}

• Command line example

drive:> "c:\Program Files\Graphviz path\bin\dot.exe" -Tbmp file.dot -o out.bmp

• Output (out.bmp)

(see above ...)