At work today, I was asked to do a sequence diagram for one of the processes we recently changed. I don't have Rose or Visio installed, so thought I would do a quick google search instead.
I came across the SD/MSC Generator. This tool allowed me to easily draw my diagrams using simple ASCII arrows. Very nice.
User->Blog: Read main page
Blog->Analytics: Register information\nabout the user
note left of Analytics: TBD\nConspriacy theories
User->Blog: Select timestamp at\nbottom of story about\nSD/MSC Generator
Blog->User: Serve up the permanent\nlink to the story
User->Blog: Click on 'Post a Comment'
The text to generate this image: