I've built a nice little bit of PHP-code serves a different signature every time you refresh the page.
I came up with the idea when I wanted to make a new signature for my forum on CDG.net. I had collected some quotes in the past from myself (vain as it may seem) that I wanted to share. Unfortunately the amount of quotes made it hard to show all at once, which gave me the rotation idea.
The rotation idea on its own isn't new; I've had forum members (I believe Darkstorn) which had a similar set-up with images of WWII planes that cycled every time you viewed his posts. Being a coder I of course wrote my own 16 lines of code which did something similar.
Getting PHPBB to accept a php file as an image requires a little creativity. I solved that problem by adding a mod_rewrite rule to access the script whenever signature.jpg is requested.
To record the sequence I place a cookie with the sequence number and up the value with every hit. The problem with this is that the cookie comes from a '3rd party', which means a half-decent browser blocks it. In order to make this work I had to make a whole friggin' P3P privacy policy and implement it! Honestly, this was more than writing the code.
Anyway, here's the result:

I've also decided to expand this little script in the near future with a simple web-interface to add and remove images from the image cycle. It might seem meaningless but I just enjoy these simple and small projects, which just give me a break from the more complex problems I face every day.