Love this jquery image zoom script, the effect is a slight zoom when you mouse over the image, the zoom reveals more of the image but at the same time reduces the size of the image and reveals tabs under the image, which in turn when clicked on reveal different images. So its a sort of tabbed mini image gallery with a cool zoom setup
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Lightbox is the de-facto standard image popup and image gallery script, lots of variants have been produced

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Another smooth image gallery, e2 gallery offers a thumbnail viewer type interface, it is really easy to use and maintain photos on a website

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