I'm working on a little sine simulator project to help me learn processing ( http://www.openprocessing.org/visuals/?visualID=44399).  Currently I have a speed control which increases or decreases the speed that a graph is drawn.  The speed is currently controlled by a framerate variable.  However, even though this speeds up and slows down the speed at which the graph is drawn, it also manipulates the speed at which you can manipulate the variables.  If you want to pause the simulation (ie. framerate 0) the program is then dead.

you can view the code & program over at openprocessing, I can't post the code here because it exceeds the max. char. count.