These 0.39 euro stamps issued by Dutch post look great:
They are made with lenticular technology developed by Lenticular Technology:
Lenticular is a specialised printing process that can show depth, motion, HD video, film or combinations of these. The lenticular material is made up of tiny ridges or lenses (hence the name "lenticular" printing). We take raw images and process them through a computer algorithm, which matches the lens surface of the lenticular material. When the two work together it enables the image to be replayed back to you.
Check out their gallery for more examples.
The technology would be great for making personalized stamps. Imagine sending a Christmas card with a short video of the family!
Via Core77 Design Blog