I have always had a deep fascination towards interactive lines, specially the ones created by Rivelazioni.com. The colors used on this one are just brilliant. This simple flash application made by Rivelazioni.com tracks mouse movements to create line patterns around the pointer. If you click on the canvas, irregular shaped circles are formed that slowly fade away.
Click Here to play around with this application in real time.
Update: If the above link does not work, click here: Alternative Link