Here is a collection of my experimental fun with circles designs. Some of the below designs are at desktop wallpaper size (colourful universe 2 series) simply click on them to get the larger sizes or see below in download section for a list of desktop sizes.
The inspiration for these initially came from this design and this one I saw on Flickr and probably my sub-conscious love of the Spirograph toy from my childhood (I used to spend hours on that ). I have added more inspirations below too.
These designs are very simple to replicate, if you want to try. I used actionscript to create about 200 circles rotated 360 degrees around with a varying gap from the centre, as shown below (but this can be done without actionscript in Illustrator). Once this was done I then took the Illustrator file created into Photoshop to add the colouring. Each of the 200 layers for each circle has a gradient overlay (as below) effect added with a hard light blend mode applied. I tried to capture the colours of a full colour wheel you see in some paint packages, like this. I then packaged this into a smart object and added a number of bluring effects and multiple layers (basically experimenting with what looked best).
Other designs from the experimental fun with circles set