I caught the tail-end of the BBC's Click show yesterday and heard about this great resource. It's called 'Dynamic Drive' and it allows you to optimise images and choose from a range of possbilites. This is what it says bout itself: 'Image Optimizer lets you easily optimize your gifs, animated gifs, jpgs, and pngs, so they load as fast as possible on your site. Furthermore, you can easily convert from one image type to another.'