Luka Matić explains why and how he designed and built a world class random number generator meeting the common standards (DIN, NIST, FIPS, ANSI) for randomness as required for cryptography and in other scientific application fields. His RNG, though designed with cheap and ubiquitous components, creates random sequences of good randomness.
An ATTiny2313 generates files of up to 4 GB of really random data, stored on a FAT32 SD card, based on avalanche noise from a Zener diode. A differential amplifier and a few analog filters eliminate deterministic effects.
More info here. Project to be published soon in Elektor Magazine.