A text2graph tool: Graphviz

Graphviz: a Text to Graph tool

Download:
  http://www.graphviz.org/Download..php

Install:
http://www.graphviz.org/Download_linux_rhel.php

Document:
http://www.graphviz.org/Documentation.php

Example:

$ cat cluster . dot
digraph G {

        subgraph cluster_0 {
                style = filled;
                color = lightgrey;
                node [style = filled , color = white];
                a0  ->  a1  ->  a2  ->  a3;
                label  =   " process #1 " ;
        }

        subgraph cluster_1 {
                node [style = filled];
                b0  ->  b1  ->  b2  ->  b3;
                label  =   " process #2 " ;
                color = blue
        }
        start  ->  a0;
        start  ->  b0;
        a1  ->  b3;
        b2  ->  a3;
        a3  ->  a0;
        a3  ->   end ;
        b3  ->   end ;

        start [shape = Mdiamond];
         end  [shape = Msquare];
}

$ dot  - Tpng cluster . dot  - o cluster . png
$ gnome - open cluster . png

More examples:
http://www.graphviz.org/Gallery.php