A great two step tutoarial with empasis on using the rotate and the brush tools in Adobe illustrator by www.bittbox.com
"Creating intricate circular designs and patterns may look difficult because the shapes can be very complicated, but you will be surprised at just how easy making these shapes can be. I will go over some neat tricks, tools, techniques, and settings that will have you pumping out perfect circular designs in no time using Illustrator." Full Tutorial