Here is part two, now with some actual measurements to substantiate that there is randomness in the machine:
http://1474orchard.ca/projects/?x=entry:entry120927-232456
I have my mega generating a batch of data that would be large enough to feed into diehard. This will take about 40 hours. I had meant to wait until that was done before posting again, but as I appear to have made hackaday, I thought I should get a move on. When I have enough data I will have a run at diehard and see what it thinks. I have been using a decent quality PRNG to simulate analogRead() data with the right distribution and using that to tune my whitening function so that it can pass diehard. I am interested to see how it works with real data.
Assuming all is well, or can be made well with a little tuning, I will neaten up my sketches and hand them over. What I have in mind is a sketch with a set of statistical tests that a newbie could use to test out the circuit and make sure it's working right. Then a short set of functions that could be used to incorporate the RNG into a project.