Jellyfish is an open source toolkit for building dynamic deep zoom applications. Usually we are using Deep Zoom Composer, client tool, for slicing deep zoom files. But if you have wanted to slice existing image source on server, you cannot use deep zoom composer at server side. Jellyfish has server side deep zoom slicer and client side Silverlight library to make dynamic deep zoom development easier. Please check the session recording, and try Jellyfish on CodePlex.
Online demo of client features : http://www.2ndfactory.com/tech/jellyfish_demo/testpage.html