Image gallery and thumbnail generator for CakePHP:
Viktor Nagy has written a tutorial about creating an image gallery with CakePHP. You can see this image gallery in action on this site: http://www.rajk.uni-corvinus.hu/~nagyv/index.php/fenykepek/index/koltozes.
The most useful part of this tutorial is in my opinion the thumbnail generator component which you can use without the image gallery.
(Via cake baker.)