Shutter Reloaded

Shutter Reloaded is an image viewer for your website that works similarly to Lightbox, Thickbox, etc. but is under 10KB in size and does not require any external libraries. It has many features: resizing large images if the window is too small to display them with option to show the full size image, combining images in sets, redrawing the window after resizing, pre-loading of neighbour images for faster display and very good browser compatibility.

http://wordpress.org/extend/plugins/shutter-reloaded/