Special Hardware Source

(rough notes that need expanding)

Zener Avalanche Noise as a source

  Zeners below 5.6V zener effect with negative temperatue coefficient
above 5.6 avalanche effect predominates with positive temp coeff
At 5.6V

Microphone/Sound Card As A Source

Not suggested for initial PRNG start-up, but okay for periodic additional seeding. If Eve has access to the sounds in your room, all is lost any way.

Resistor Thermal Noise As A Source