Lightview is a Prototype/Scriptaculous
image viewer with adjustable rounded corners, smart image resizing, build in slideshow and works on all modern browsers.
Nick Stakenburg has released Lightview v2. With Lightview v2.0 you can also overlay video (Quicktime), Ajax, Flash .swf, iframe and inline content.
Download and include Prototype 188.8.131.52 and Scriptaculous 1.8.1 in your header. If the filesize is to big for you, with Protopacked you can have the required files, Prototype and effects.js, starting at 28kb.