Gray code at the pediatrician's office
blog.plover.com
See http://blog.plover.com/math/gray-codes.html for the Perma-Link.
blog.plover.com
http://en.wikipedia.org/wiki/List_of_fractals_by_Hausdorff_d...
If you like numbering systems, you should read the book `Purely functional datastructures' by Chris Okasaki. The book has nice chapters on the link between number systems and data structures.
Or see the lecture on Skew Binary Numbers (http://www.cl.cam.ac.uk/teaching/2004/IntroFuncProg/lecture0...) to get tho flavour.
(The PhD thesis on which it is based is available at http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf)
It's an interesting article, and worth a repost.