Launched TheInvisibleAd.com today. It's my version of the amazing Million Dollar Homepage and is mostly JavaScript muscle flexing 
There is a little PHP, but very little, some style work and some AJAX/XML. But most of it is the JavaScript.
Will share the implementation details here, watch this space. There were a few issues to resolve … trying to dynamically create 75 * 42 nodes in a DOM tree is one example.
Again - http://www.theinvisblead.com.