The best tutorial on making realistic looking tattoos on skin (or any surface). This works with black/white and color tattoo's.
Keep foreground objects in focused and clear while making the background blurry.
Erase tattoos, jewelry, and objects from photos using the clone tool.
Fast Forward past the first 45 seconds of this video.
Learn how to use the iwarp filter for squishing, stretching or growing images in weird ways. Good for making funny faces.
Demonstration on how to apply filters to shapes.