Simple hardware RNG

Question

I made a tongue-in-cheek comment to this question about making a hardware RNG.

Does anyone know of any simple plans or can anyone describe a simple hardware based RNG and the software to drive it?

Go to Radio Shack. Buy a diode, an NTR resistor, a capacitor and serial cable. Cut off the end of the serial cable that does not fit on your computer. Solder the diode and resistor in series between pins DTR and DSR of the cable. Solder the capacitor between DSR and TXD pins. Write a small C program to do the following: Set DTR to 1. Start Timer. Monitor DSR until it goes to 1. Stop Timer. Calculate resistance from elapsed time. Retrieve several bits from that value to use as part of random number. Repeat until enough bits have accumulated.

Answer 1

If you have a Linux box, you already have /dev/random.

Answer 2

Diode shot-noise is pretty good. Amplify, A/D convert and sample.