Encrypting any kind of data storage?

Hi

here's the situation: I need an EASY (or at least scriptable) way to 
encrypt/decrypt every single "sector" on a given storage device (flash 
drive, hard drive, floppy disk etc.pp.). Ideally that would be done 
using a boot disk (boot CD, flash, floppy...). Any suggestions on how to 
do that securely?

Also, does anyone know of any good research paper on recovering (or 
prevention of recovery) of overwritten data on various kinds of storage 
media, i.e. which one is safer? magnetic vs. optical vs. electronic?

Thanks
Jens