Photomanipulation/Photomorphing Techniques

Since nobody has started one yet, I thought I would do the honours. The thread is for any photomanipulation technique. Just to be clear, "photomanipulation" doesn't mean "pasting two images onto a background", it means changing images to make them look like something different, whether it's by distortion, re-colouring, re-texturing, or careful creation of a scene by layering images into each other, with transparency effects, etc.

I'm making the thread open, so it can be used for any program capable of the appropriate photomanipulation techniques - the two most notable being GIMP and Photoshop (in no particular order).

Now, down to business.

I've made a tutorial for how to use GIMP to do basic transformation images such as those found in my deviantart. You can find the tutorial here (direct link to image - didn't post as an image because it's quite large, at almost 6000 pixels tall). The image that was created for that tutorial can also be seen here (again, a bit large to post directly).

I'd like to hear other techniques - I know of at least one more, which is in use by SkyJaguar on deviantart (link, and involves a layer-by-layer technique for making hair/fur using the smudge tool. I would also recommend that prospective photomanippers read her "tips for awesome photomorphs" (link near end of the "how to make fur" tutorial).

I generally just play size comparison games.When Dennis Nolan
did the BEFORE and AFTER for Yolens transformed
heroine Dove Isabeau he set her image against the same wall in the
witch's tower.Once you get the background of the two pictures matched
up,it's possible to figure out just how big serpent Dove is after her initial
transformation.(about 5 feet from the floor to her shoulder blades)After that
each time she gobbles a knight her size increases by 1X

Hence after 99 knoghts she's 99X bigger then she started as.