Seadragon & Deep Zoom
I stumbled upon this today and definitely want to play with this further when I have time....
SeaDragon Ajax
http://livelabs.com/seadragon/
"The aim of Seadragon is nothing less than to change the way we use screens, from wall-sized displays all the way down to cell phones,
so that graphics and photos are smoothly browsed, regardless of the amount of data or the bandwidth of the network."
Deep Zoom Composer
"...a tool to allow the preparation of images for use with the Deep Zoom feature currently being previewed in Silverlight 2. The new Deep Zoom technology in Silverlight allows users to see images on the Web like they never have before. The smooth in-place zooming and panning that Deep Zoom allows is a true advancement and raises the bar on what image viewing should be. High resolution images need to be prepared for use with Deep Zoom and this tool allows the user to create Deep Zoom composition files that control the zooming experience and then export all the necessary files for deployment with Silverlight 2."