Graphviz

Neato

"spring model layouts. This is the default tool to use if the graph is not too large (about 100 nodes) and you don't know anything else about it. Neato attempts to minimize a global energy function, which is equivalent to statistical multi-dimensional scaling. [source http://www.graphviz.org/]

graph G {
    run -- intr;
    intr -- runbl;
    runbl -- run;
    run -- kernel;
    kernel -- zombie;
    kernel -- sleep;
    kernel -- runmem;
    sleep -- swap;
    swap -- runswap;
    runswap -- new;
    runswap -- runmem;
    new -- runmem;
    sleep -- runmem;
}