How can we render graphviz diagrams in drupal pages? I'd like to be able to allow users to insert Graphviz images in Drupal comments and Wiki pages.

What's involved it doing this?

The benefit is that users could enter something like the following snippet to see a graph.

[code lang=graphviz]
  digraph G {
    a  [label="Hello", shape="square", URL="http://en.wikipedia.org/wiki/graphviz"]
    F1 -&gt; a[label=".63"]
  }
[/code]
There's the Graphviz Filter module, which provides an input filter that will convert Graphviz DOT syntax to the required diagrams. You can find more information in the Drupal documentation on graphing modules.