Here's one I worked on a while ago and just dug out to play with.   It still needs work, crashing on the occasional illegal value, but I wanted to share it with a few people when I found it.  

This program creates a primary circle, but it only calculates the points on the circle without printing them.   It uses these points as the centers of secondary circles, which it prints.   This results in a Spirograph-like drawing, but with separate circles instead of one continuous spiral.   Change the sizes of the circles, and the starting and ending angles to use, and get some neat images.

Until I can add instructions to the program itself:

Change the values in the Primary and Secondary windows and click DRAW or hit ENTER.   The CTRL key turns on and off the ability to control the values with the keyboard.   Up and Down arrows to select the parameter to be controlled, and left and right arrows to change the values.   A slider control appears in this mode, and you can use it with the mouse to change the values also.   The image redraws automatically in this mode, so the picture "morphs" as you watch.   The Rotate checkbox causes the perspective of the Secondary circles to change according to their position on the Primary circle, giving them the look of a Slinky from various angles.   Give it a try, it'll be clear when you see it.

The Frame Grabber function is a way to save an individual creation to a filename.   Enter a prefix, and sequentially named files will be saved.   I use another program to make these into cool animations, a feature I'd like to add to this program.  

The Clear button does what it says. The checkbox causes the image to be cleared (or not) before redrawing.

Favorites is a future feature, where you can save and recall the SETTINGS you used for a drawing, so you can use them as a starting point for further experimentation.