SoarPort is a free image hosting service for large dimension images. You can upload a large image, and the result is the image is presented in the SoarPort viewer (which makes you image work in much the same way as Google Maps).

 The  SoarPort viewer is also free, and you can embed it within any of your own webpages. This saves you on bandwidth charges for trasnferring images to your audience. It also presents the real image in a convenient way: people do not have to leave your page to see the image at its full size.