The challenge was to make a card game in the browser using only HTML, CSS, JavaScript, and the bare minimum of images. What came out of it was a full-fledged JavaScript object framework for card games using lots of HTML and CSS, but only three images (four if you include the card back), and a single card game (a solitaire variant) implemented in this framework. You can try it out here.
Of course, that doesn't involve AJAX, and the project is called AJAX Cards. Current development is on a Ruby on Rails backend for an XML-RPC-based game protocol, and associated extensions to the existing JavaScript frontend. The new backend and frontend extensions should be in CVS some time in April 2006. In the meantime, visit the project page at SourceForge.