http://www.strike-the-root.com/51/walker/walker12.html
Came across it pretty randomly, I found it quite intriguing. Cryonics is "routine" for human embryos, not far-fetched for humans at all. Makes the whole thing seem potentially very reasonable (and me someone who hasn't signed up and doesn't plan to).
Don't confuse cryobiology with cryonics. Cryobiologists, the people who actually invent these tissue preservation techniques which are routinely used in hospitals and research labs all over the world, typically think that cryonics is a pseudoscience at best and a fraud at worst: http://en.wikipedia.org/wiki/Cryobiology#Scientific_societies
Reversible vitrification of individual cells or small samples of tissue is possible because they are small, thus they can be cooled quickly. Cryoprotectants are used to facilitate the process, but not in toxic concentrations.
Fast cooling of objects as large as a human body, or even a human head, is essentially impossible due to the square-cube law: the thermal capacity of an object is proportional to its mass, which, for a given density, is proportional to its volume, while its capacity to transfer heat is proportional to its surface area. As size increases, surface area grows quadratically while volume grows cubically, hence their ratio decreases.
If you attempt to cool a large object too fast, you will freeze or vitrify only a thin superficial layer, and probably even shatter it, since temperature gradients cause gradients of thermal contraction resulting in mechanical stress.
Cryonicists who attempt to preserve whole human cadavers or heads, perfuse them with large amounts of cryoprotectants in order to achieve vitrification. This has several problems:
Um, the whole point of the blood system is to overcome the squared area vs cubed volume problem. So you can cool larger things fast if you use blood vessels to move fluid that carries out heat.