This is a custom ASP control I made to allow uploading and resizing images using AJAX. When you instantiate the control you can specify the maximum width and height to save space. For this demonstration I made it 600x500. If the uploaded image is bigger than that, it will start by proportionally resizing to that area. The recommended size is specified on the resize call and is used as a suggestion to the user. It's able to read png, jpeg, gif, and bmp files, but will only save as jpeg or png. I've tested in IE 7 and Firefox, but make no guarantees about IE 6.
Side note: That's me at my company's halloween party in the sample image above =).