Diagramming tool integrations? PlantUML, svgbob, graphviz, etc

Woah, svgbob is really cool – thanks for clueing me in.

It would be pretty cool to encode the diagrams as plaintext in markdown files, and know either the .md file or the rendered .html would be readable and complete. However, it doesn’t seem like the most urgent inclusion. Who really needs to distribute their plaintext .md files?