The Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, have developed a set of wonderful medical animations that they collectively show on their WEHI-TV. You can see animations on DNA structure and function, malaria, colony-stimulating factors, apoptosis and other stuff. If not all of the animations have ended up on youtube just yet, they will sooner rather than later, but I certainly recommend the animations at WEHI if you want high picture quality.
*****
The brain – http://chosetec.darkclan.net/origami/
WALL·E - http://chosetec.darkclan.net/origami/