Deprecated: Check out https://github.com/fedealconada/Leaflet.AffineImage
@fedealconada greatly improved this by making it an actual leaflet layer, which is much better; you should use his instead. This repository remains for posterity.
A super-hacky overlay for leaflet that lets you display an image on top of the map, transform it using three anchors, and output ground control points you can pass to gdal_translate. (Rule #2: Inspired by Chris Broadfoot's overlay-tiler.)
This should probably end up as a Leaflet layer object that you can add with map.addLayer(), but until then, there's this joint.
Look at index.html and style.css for a usage example.
Works in Firefox 10, and Chromium 17. Probably breaks on some other browsers.