random?
if it really doesn't have to be truly random, the simplest circuit is a pseudo-random, maximal length linear feedback shift register. Look up LFSR on Google and you'll quickly find some circuits. It's basically a serially connected line of flip-flops with strategically placed XOR gate(s) providing feedback. Sampling a relatively long shift-register sequence, (n=127 for ex), will provide an essentially random output. Sequence repeat times of trillions of years (assuming the computing power common on todays machines) are easy to generate. The hard part is coming up with the feedback taps (prime over the Galois field, whatever that means. Damn it Jim, I'm an engineer, not a mathematician). Fortunately, the work's already been done for you and it's available on the web. I don't have the website handy, but a very generous minded mathematician (french, I think. I ran across it about 9 months ago) has posted all taps up to 512 or so on his website. Again, do a google search. Good luck.
- CAL