Seadragon is Deep Zoom implementation purely using JavaScript without Silverlight. You can zoom in/out using mousewheel and drag it to pan arround as sample picture below.

To create seadragon like picture above, you can upload your image to http://seadragon.com. You will receive unique URL after uploading images is done which can be embedden to your web page. Seadragon will automatically checking your machine. If you have Silverlight installed on your machine, Silverlight version will be used. If Silverlight is not installed yet, Seadragon will use javascript version.