To create a “zoomable” web image in Photoshop CS3 or newer, open any image then go to File > Export > Zoomify.
This plugin creates a Flash object that sits within a web page that allows users to freely explore the image. Users are allowed to zoom in and out, and pan around it. Photoshop generates all the necessary files, so you don’t need to know HTML or Flash to take advantage of it!
This is a great way of displaying your high res images online without running the risk of other people downloading the original file.