A small sampling of ideas that I have actually gone on to make:
A catgorised collection of interesting links that I really mean to read later
A static site generator written in dear old PHP. A little neglected I must admit.
Simple site that will detect your browser and tell you how to clear the cache
Some old tosh when I thought I could play the guitar
A Habari powered portfolio site with a bit of Flickr and Tumblr integration
I love sandwiches. I love websites. Here is a glorious union of the two... and also an excuse to rant about sandwiches in London
Comments and corrections to @edvanbeinum