Similar in nature to GifOptimizer, GifBot will shrink your graphics to enable faster page loading. One drawback to this service though... the image you want to shrink must be on the web. If that's not a problem, then by all means check them out.
This is one more online graphic optimizer, but this one is limited to jpeg images only. Since the vast majority of images in use on the web are GIF's, then this one may not be useful for you. Nonetheless, it's still a great free service with all kinds of neat options...give it a try.
GifBot
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Graphic Reduction
