PicLens
Installing it places a button on the Toolbar. When you're on a PicLens-enabled Web site, click the PicLens button to activate the PicLens interface. No doubt, PicLens puts the "graphic" back in "graphic user interface." However, it doesn't work on every Web site. It requires back-end code to be installed on the server hosting the site in question, and so the plug-in only supports a handful of the most popular graphics-intensive sites such as Facebook, MySpace, YouTube, Picasa, Flickr, and a few others. A WordPress plug-in allows users of that blogging system to create PicLens functionality, and there's a Webmaster's guide on the PicLens site for users who host their own sites.
Internet Explorer version, and Safari support is extant but not extensive. Even though PicLens is best used with Firefox, installing the add-on is worth it just for the sweeping, futuristic way that images stream by when you browse.