Nadim has released Asciio, a Perl/GTK application that lets you draw ASCII charts using a GUI. Objects on the screen are sizable and have all the properties you'd expect in a drawing tool (titles for the boxes, bullets, etc), but the end result is plain text that's embeddable in your code.
Here's the first of two screencasts that give you a feel for its capabilities.
Nadim says "I find myself starting it quite often just to draw a little diagram that helps me write better Perl code. Then I can keep it in the code itself."
That's pretty cool, but holy crap that screencast is too long. Just a 30-60 second "Woohoo, Look at Me!" would be excellent.
I've just used Asciio for the first time and it was a piece of cake - and delicious cake at that!
Now I don't have to dig through my paperwork to find state transition diagrams to explain to me what my code is about - I can just put the diagram in a comment.