PicLens. It basically allows you to view images from sites such as Google image search or flickr in beautiful full-screen glory, complete with a thumbnail navigator at the bottom and slideshow features. It integrates itself with Safari quite elegantly. If you're viewing one of the sites that it supports, a little icon appears upon moving your mouse over an image, clicking on which makes the image zoom to full screen.
Now zooming low-res images to full-screen wouldn't look so nice. Luckily for us, what makes PicLens so good is the fact that it is clever enough to load the high-resolution image that is linked on the page and not the [in most cases] low-res one displayed.
Although it currently works only with a handful of sites, those are probably the ones that you do your major image viewing on the web anyways. Even if that's not the case, you should definitely give PicLens a try.
Update: Just found out that it works with the Apple remote too!