The Cryonics Thesis - - The why of cryonics, as understood by the Cryonics Institute.
Nanotechnology and Cryonics - - An introduction by Jerry Emanuelson of Colorado Futurescience. 3 printed pages.
Ralph Merkle's Cryonics Introduction - - Short and useful, but not really "simple." It assumes some knowledge of cryonics already, so read some others first. 3 printed pages, with several internal hyperlinks to other explanations or web pages.