Nature is full of spirals. In the header of this blog I’ve chosen three from different sources. The first is a fiddlehead fern, before it unclenches into its mature state. The second is a prehistoric petroglyph, showing an ancient human fascination with spirals. The third is a nautilus shell, which gives us an example of a Fibonacci spiral.
Leonardo Fibonacci was an Italian mathematician who, among other things, brought Hindu-Arabic arithmetic to the West. Here are a few links for more information.
Wikipedia entry on Fibonacci
Waaay in depth material on Fibonacci numbers and more
Also, a Google image search for “Fibonacci spiral” brings up all kind of interesting things!